Since Android 15 (FP5.VT28.C.042) my Bluetooth connection with my car drops within minutes

Applied last update to my FP5 to FP5.VT28.C.042 and now my Bluetooth connection in my car drops right after 2-3 minutes, while I’m listening to audiobooks on Audible. Then reconnects again. It was working fine before the update.

This is unusable.

Also I noticed, that the car does not get author and other information right from the phone (though the chapter number does work on Audible).

What can I do?

I guess I cannot revert the update, can I?

If you bootloader is locked, then no (without a factory reset).
If your bootloader is unlocked or if you unlock it (which forces a factory reset) you might try to install an older version. But as the update was afaik a major upgrade, it might be necessary to delete all your data anyway (possibly an older major version has problems with our upgraded data).
So I think your chances are better if you report the problem to support.