Add another person having the same horizontal line problem at night. Power is at 97% and wifi RSSI is -41 which is smoking hot since the WAP is just on the other side of the door.
There are enough of us getting the exact same problem. It must be some sort of software or firmware issue. Can you get this escalated to engineering for review, please?
If this many people are having the issue here, there are at least 25x more people out there having it but not posting, probably more.