After checking for updates, the APP requested a firmware update for the ACCU, then the FLYSave DB had to be updated and then the error "Firmware not compatible" was displayed ...
First of all, turn everything off, so turn off the drone, turn off the remote control, close the app and restart everything ...
See there are no more error messages, everything is fine!

A short test flight in the room and of course immediately collided with the couch ... After this (thank God soft) crash, the drone was almost impossible to control. She kept drifting in one direction. Hopefully nothing is broken now ...
Turn everything off again and start over again - and lo and behold, the drone is lamb-pious again and does not drift - everything is fine!

What I mean by that - if the drone behaves strangely, a restart often helps (sometimes removing the battery and reinserting it).

Had kind of same problem. Update flybase at the same moment of the update of the fly app. Result "incompatible firmware". Except restarting didn't help much.
First updated the flybase of the drone with the Assistent. Then the update of the fly app went smoothly.
Didn't had an unstable flight. But having two updates at the same time seemed a bit too much.

Hello there ozoffi. I am sorry for the trouble this has caused and thank you for reaching out. Since the said drone crashed and if you feel that the said DJI drone is not preforming well on your future flights. I would recommend to contact our DJI support team at  https://www.dji.com/support for further assistance and for us to be able to check the said drone thoroughly for damages. Thank you and fly safe always.

Since the drone is working properly again, I rule out any damage (what should be broken if the drone flies against soft upholstery and crashes into soft upholstery?)
I just wanted to say that with this type of behavior, a complete restart of the drone (possibly removing the battery and reinserting it), remote control and mobile phone / app often helps, before you panic and suspect the worst.