@Lazar-Demin Now I observed after retest in working device I got the menu as expected from your mentioned steps:
log as below

b) On the stuck devices:
but on a stuck devices device it's no change, observed as same logs which updated earlier for not working device:
I performed the same steps (multiple times) as with the stuck devices. The stuck devices remain in their frozen state, displaying the same log output as shared earlier for not working device log.

Observed Behavior
The device fails to boot correctly, getting stuck in bootloader mode with a steady orange LED and no hostname availability.
Only a partial boot log is available after the mentioned steps followed.

log as below:

Board: Onion Omega2 APSoC
DRAM: 128 MB
relocate_code Pointer at: 87f60000
flash manufacture id: c2, device id 20 19
find flash: MX25L25635E
*** Warning - bad CRC, using default environment

@crispyoz Thank you for sharing your experience.
I’m using the Omega2+ (through-hole version) on a custom PCB, which already has an SD card slot below it.
**Do I need to configure anything on the software side for the SD card, or can I simply insert the SD card and start using it?

If any configuration steps are required, could you kindly share them with me? Your guidance would be greatly appreciated.**

@Lazar-Demin Thank you for your detailed response and suggestions.

Updates and Observations
Setup: Using a custom PCB (not an expansion dock).

1) File Writes to /tmp
Following your suggestion, I have updated the setup to move all file writes to the /tmp directory. This is intended to prevent flash wear and file system corruption.

2) Recovery Attempts on Devices
I currently have three stuck devices.

a) On a working device:
I followed the recommended steps: powering on while holding the FW_RST pin (GPIO38) active.
Observation: This process erases the existing firmware on the working device, resets it, and allows me to re-upload the firmware. After this, folders become accessible, and the hostname is visible.
I did not see a bootloader menu during this process; it directly erased the firmware and enabled reconfiguration. In short working fine

b) On the stuck devices:
I performed the same steps as with the working device, but there was no change. The stuck devices remain in their frozen state, displaying the same log output as shared earlier:

Board: Onion Omega2 APSoC
DRAM: 128 MB
relocate_code Pointer at: 87f60000
flash manufacture id: c2, device id 20 19
find flash: MX25L25635E
*** Warning - bad CRC, using default environment

Current Status:
Following your suggestion, I updated the file writes to /tmp and the device is under observation for 8 to 10 days (as my old device is got stucked after 8 days).

Do you have any further suggestions for recovering the stuck devices, given that the bootloader menu doesn’t appear to be accessible? Could there be an underlying hardware issue contributing to this behavior?

I look forward to your advice.

@crispyoz Thank you for your detailed response and suggestions.

1)Omega2+ Version Confirmation:
I am using the Omega2+ (through-hole version), not the Omega2S+ (surface-mount).

2)RAM Corruption and Shielding:
Your observation about potential RAM corruption due to inadequate shielding, your point number 2 and 3 are insightful. I will investigate the custom PCB design to identify any potential interference or shielding gaps that might be causing the problem.

3)Script Behavior and Potential File System Corruption:
I suspect the scripts might also be contributing to the issue. For clarity:
The main_app.py script captures Modbus data packets (32 packets of 105 bytes each) and appends them to an Excel file every 2 seconds. It then publishes a JSON string (~3147 bytes) via MQTT every 5 minutes. It handles reading Excel parameters, connecting to MQTT, and clearing processed data.
The check_system_status.sh script monitors the system and triggers a reboot if main_app.py encounters issues like corruption or logging failure.

Important Observation:
The last log observed before the device got stuck in bootloader mode occurred immediately after executing the check_system_status.sh script which executes only if the main_app.py got corrupted/failure in data logging.
so auto reboot was provided in the same .sh script and it got stucked from then only.

Recovery for Stuck Device:
Could you provide detailed steps to recover the device stuck in bootloader mode?
for the below Observed Behavior
The device fails to boot correctly, getting stuck in bootloader mode with a steady orange LED and no hostname availability.
Only a partial boot log is available after resetting.

@crispyoz thank you for looking into my issue.

Log Details:
The logs provided above are from the same Onion Omega2+ device, captured before and after it got stuck. The working log corresponds to the device’s state before the issue occurred, while the not working log was generated after it got stuck.

Dock Information:
I am not using an expansion dock. Instead, I am using a custom PCB, which has been thoroughly tested and verified for compatibility with the Omega2+. Both the non-working and previously working Omega2+ units were tested on this same custom PCB setup.
apart from this the Omega2+ is monitored using Docklight. I am using the same Docklight v1.6 setup for both the working and non-working states of the Omega2+ unit.

Reset Button Attempt:
I have attempted holding the reset button while powering on the Omega2+, keeping it pressed throughout the startup process, for 10-15 seconds and repeatedly pressing the Enter/Space bar keys to exit boot mode. Unfortunately, this did not resolve the issue. After releasing the reset button, the orange LED remains steadily ON, and the device fails to move beyond the bootloader mode.

Power Source:
I have verified that the power source is stable. The same power source is used for both the working and non-working states of the Omega2+ unit, ruling out power-related concerns.

Testing Another Omega2+:
To further investigate, I tested a fresh, new Omega2+ unit using the same dock and power source. Initially, the new unit worked fine. However, after 7–8 days, it exhibited the same behavior as the previous device, with identical logs indicating it is now stuck in bootloader mode.

Dock and Power Source Consistency:
The same custom pcb and power source were used to test the Omega2+ unit both before and after it got stuck. This confirms that the setup is consistent across both states.

Product Being Used
Device: Onion Omega2 APSoC DRAM: 128 MB
Carrier Board: Onion Omega2+
Firmware Version
Firmware:
UBoot Version: Unable to retrieve as the device gets stuck during boot.
Below details got from the same device while it is in working mode (in detailed log named as Onion_Omega_2+_Normal_Working_log.txt)
Image Name: MIPS OpenWrt Linux-4.14.81
Linux version 4.14.81 (root@c34dd7d43957) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r0+7498-730f2344ba)) #0 Fri Nov 25 04:10:54 2022

Description of the Issue and Context
The issue occurs after running custom scripts (main_app.py with main program and check_system_status.sh for auto reboot) through /etc/rc.local.
The device gets stuck in bootloader mode after running for 8–9 days with the following conditions:
An orange LED remains constantly ON.
The device hostname is not available, and the usual Onion Omega2 UBoot Version log does not appear during boot.
Internet connection was working previously, but the device is currently not connected to the internet.
Resetting for 10–15 seconds only resets the device momentarily, with the orange LED returning to a steady ON state.
Log after reset

/ __ ___ ()__ ___ / __ _ _ ___ ___ ____ _
/ // / _ / / _ / _ \ / // / ' / -) _ / _ /
///////// /////, /,/
W H A T W I L L Y O U I N V E N T ? /__/"
Board: Onion Omega2 APSoC DRAM: 128 MB
relocate_code Pointer at: 87f60000

21-11-2024 14:32:08.90 [RX] - flash manufacture id: c2, device id 20 19
find flash: MX25L25635E
*** Warning - bad CRC, using default environment

Expected Behavior
The device should boot normally, display the hostname, and show the Onion Omega2 UBoot Version during startup.
and other logs as mentioned in the attached file Onion_Omega2+_NotWorking.txt.

Observed Behavior
The device fails to boot correctly, getting stuck in bootloader mode with a steady orange LED and no hostname availability.
Only a partial boot log is available after resetting.

Steps to Reproduce the Issue
Configure the device to execute main_app.py and check_system_status.sh via /etc/rc.local.
Let the device run for maximum 8–9 days while performing normal operations.

Reboot the device.
Observe the device failing to boot properly and entering bootloader mode with a constant orange LED.

What's Been Attempted to Resolve the Issue (But not working)
Reset the device for 10–15 seconds.
Result: The orange LED remains steady, and the boot fails as before.
Verified the /etc/rc.local configuration for any errors.
Attempted to re-establish an internet connection without success.

Help Looking For?
Steps to recover the device from its current stucked bootmode state.
Assistance in diagnosing the issue with the bootloader or firmware.
Guidance to prevent this issue in the future.
#############################################
Normal Working Log (Before Failure)
[0_1732531326774_Onion_Omega2+_Normal_Working_log.txt](Uploading 100%)

Not Working Log (after Failure)
[0_1732531366575_Onion_Omega2+_NotWorking.txt](Uploading 100%)

Also attaching log images of working and not working device below

I am unable to access the bootloader command line on the "stuck" device. After a reset, I can only retrieve the log from the port, as mentioned below.

I followed the steps to activate Web Recovery Mode, but the U-Boot version is not displayed. After resetting for 10-15 seconds and repeatedly pressing the Enter/Space bar keys to exit boot mode, I still see the same log as shown in the previously mentioned image ("################## ONION OMEGA2+ ISSUE - Not Working Device") and do not see the menu option.

/ __ ___ ()__ ___ / __ _ _ ___ ___ ____ _
/ // / _ / / _ / _ \ / // / ' / -) _ / _ /
///////// /////, /,/
W H A T W I L L Y O U I N V E N T ? /__/"

Board: Onion Omega2 APSoC DRAM: 128 MB
relocate_code Pointer at: 87f60000
flash manufacture id: c2, device id 20 19
find flash: MX25L25635E
*** Warning - bad CRC, using default environment

Could you please guide me on how to recover the "stuck" device?