Only from the start to the 'bootconsole [early0] disabled' lines I got this:
That suggests that the issue is with U-Boot's configuration of the UART, rather than the configuration Linux eventually establishes when it starts using the serial port in the way it will when fully booted.
As I've said before, slight innacuracy serial baud rate may be the issue, especially if it shows up with some things on the other end of the serial cable and not others. There are various ways of configuring baud rate generation in the MT7688 UART, some of which will give more accurate results than others.
Other suspects include loose connections, or power situations where some of the supply return current is flowing through the serial connection's ground, introducing a voltage drop there and thus difference in effective ground levels. The observed early vs. ultimate console difference would seemingly point away from that possibility, but then power consumption is different at different points during boot.
@WereCatf so basically all of the 3.7V LiPo batteries found here can be used. Surely a low Ah model will last few but will charge faster than a bigger one. My concern is about the charging current available: if I use an high Ah model, my power dock will charge it without overheating?
It's not the capacity that determines the charging-speed, it's the charging-circuit that does. A 500mAh battery will charge at the same speed as a 2000mAh one, so it'll just simply take longer for the bigger battery to get charged full. That is to say, you could safely slap a 20,000mAh battery on it, if you wanted to
@None-None nice. i will take a look at the whole circuitry when im back from holidays in 4-5 days!
But my first guess would be that (although i havent looked into its circuitry) that the protection circuit also discharges the battery? because normally you want them to be at ~70% of their load when storing them
@Shamyl-Mansoor now it would be good to check the boot log ... is there a possibility to generate one and write it to a separate file?
I know, without uart chip on the board this will be not so easy...