I experienced exactly the same what other people have already reported: The tablet has been fully charged, and then it freezes (crashes). A soft (!) reset (on/off + volume down) is always necessary.
Seems to be an issue of the OneUI 8 update. Please don't answer with predefined text patterns a la 'clear app caches' etc. as all those hints do not work.
Here are several references with this severe bug. Everybody with a A9 or A9+ tablet experienced the same and nobody found a solution so far:
