Get some diagnostics Ista D and the standard tools suite.
Have somebody hold the fob close to middle of the rear window
while opening it. The diversity antenna is there.
With diagnostics you can test stuff without taking it apart.
If it was doing this one side of the car and not the other you might
be right but if its both sides a diversity antenna problem would be
more likely .
https://www.newtis.info/tisv2/a/en/
diagnostic manual ista/inpa
https://bimmerprofs.com/diagnostics-inpa-part-1/
https://www.google.com/url?sa=t&rct=...xo19teM9vkTF-C
https://www.google.com/url?sa=t&rct=...7x8H3pN8h1fMuF
https://www.bimmerforums.com/forum/s...-P-actually-do
There is some theory on the Comfort access in the electrical pdf's
electical e90 pdf
http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU
georges links
https://www.bimmerfest.com/forums/at...9&d=1539905743