Thanks @Luciano-S for linking that thread, I was just looking for that! One of our other community members in that thread also explained that the contact surfaces may be micro-welding when contacting/separating due to high current. He advised to activate/deactivate the relays a couple of times so the contacts would become smoother and less likely to micro-weld: http://community.onion.io/topic/784/resolved-relays-sticking/20. See if that helps and let us know. Gabe