Are you using the updated version of Lightroom mobile on your tablet?
It seems that Lr is freezing while attempting to sync those 8500+ images.
How much space do have free on your tablet?
Have you tried clearing App cache and signed out of Lr mobile app?
I tried clearing the cache and signed out of LR to no avail. LR was again freezing after a short while.
From what I could see from the UI, was done synchronizing.
Now I uninstalled LR altogether and re-installed it.
I made sure I configured it right away to use the external storage.
Then I signed in.
The issue seems now gone.
I will keep you posted if the issue resurface.
To sum up, a re-install seems to have fixed the issue.
Thanks, Christophe. Glad to know issue is fixed. Keep us posted.