In a week passed since the last firmware upgrade, all the thumbling reports disappeared. Has this problem been solved? No thumbling anymore?

It has not been fixed.
DJI added detection of the tuble to the avata, and now it prevents crash by "braking" at that point and going to N mode and going in hoover for just a bit.

Several youtubers have tested this and also were (in some cases) still able to crash the avata in tumble