We figured it out, it was wrong paht to skeleton, I apologize, ticket tan be closed/rejected.

but what exacřtly control if animation should froze?

tried multiple combinations, and all worked in 1.29 and before for years

what settings is responsible for that behaviour? what is needed to change in xob, config, p3d model, skeleton or somewwhere else?

import work only in game root folder not for fbx files which are in subdirectory

It is not a bug for reporting here, It just issue which can happen every update, thats why is there experimental stage. BUT NOBODY helped test my mods in experimental stage. So please close this ticket, it nothing related to vanilla game but mods which people rejected testing.