Is your printer enclosed? I know petg tends to warping, some glue or slow first layer could fix, but enclosure would be good anyway.
Glad you found a solution for your connectivity issues.
Did you ever turned the filament loss or grinding protection off to see if the weird behaviour come from this protection features?
I’m no U1 owner so, some more guessing, maybe print without the feeding motor on the side for troubleshooting?
I’m wondering, it seems there are not many people printing petg on the U1..
This similar setting was told you by support, right?