v5 C6 stick keeps tripping the system

[OmidTahouri]

I tried to piggyback on an older thread with two posts, but didn't receive a response so I'm starting this thread here.

tl;dr:

• stick worked fine for ~5 weeks but now causes a power trip or "Communication fault"
• I have the indoor thermostat on the wall as well as an outdoor temperature sensor connected to the ebus terminals - all stable for 10+ months since the system was originally commissioned
• now, whenever adding the stick back to the ebus terminals, it keeps tripping the whole system or causing the main unit to display a "Communication fault" message

More details are in the thread linked to above. I really want to get it connected again (and unlock it/buy the activation key), but I'm not sure what else to try and don't think it's healthy for the system to keep trial-and-erroring to find out.