Maybe it stops charging if humidity is detected, similar to the “moisture in charging port” warning that can appear on the phones.
It is interesting to me that the crease goes away once the screen is disconnected. That almost makes me think the crease is caused less by the folding itself and more by how the parts are supporting the screen.
It is resin encased, not very easy to do.
The modems are intel
Did you miss step 3?