Hi!

I'm new here.
I had similar issue with my friend BMW e39 530d where diferent car modules were not working correctly. Couldn't connect with central body electronics module and A/C started with delay and front turn signals started to act as corner lights. Also air suspension self level didn't work.

There were more issues but the solution was kinda bizarre.
Overall, problems started when it was raining and lasted for several days after rain. Then after that everything was OK. When faults were present and I scanned car with BMW scan, then I saw K bus fault in instrument cluster.

You don't believe but k bus fault was generated from webasto. Unplug webasto and K bus voltage rised up again and car worked fine. You can't just remove webasto fuse because k bus is still connected and shorted. Additionally you can disconnect webasto k bus from slicer behind glovebox and over central body electronics module to be sure that webasto k bus wire is not shorted to body. This could happen... Ow, by the way, when car was acting fine, then webasto was also working fine.

Best wishes
Edward