Just made an account to come on and say I’m currently having the exact same problem, with the same frustrations. PO of car had sunroof replaced and liftgate module replaced, and those drains are clean. Cars always been fine if the weather is dry for a few days, but any rain storm killed me. Cleaned firewall drains, let the car dry, no issues at all the evening of the cleaning/drying.

Go out the next morning to move it, and to my huge shock, errors galore. iDrive screen flicker is terrible, blinkers don’t work, climate control issues, etc etc. same exact issues

Please keep posted if you figure out the issue with yours, and I will do the same. It seems feasible that one of the DME connections could be screwy since I had to contort the wires to get the tub out to access the firewall drains. Will go check after it quits raining ��