I only have the 3.1 Felix printer for less than two weeks but I still could not print anything that was finished, or finished well, this forum was helping a lot to resolve issues so far, but now I'm at the point where I'm stuck. So here is what happened... the print just went fine till a point when ...

I realized that the extruder was causing the issue, should not assemble as in the assembly instructions, I needed to separate the heating cables from the temperature measuring cables and the print never ever stopped again. But I'll keep in my mind if any comm issue comes up to check with a different...

I just bought a 3.1, and I experienced the same issue. Did you ever figure out what was the root cause?
Thanks,
aladar