High CPU usage will occur overnight during scheduled tasks.
The most intensive processes are optional and are found in Settings → Library
I’d say from that picture that VPTs and Sonic Features are the big users, with Loudness next.
My TS-451+ with an old Celeron J1900 from like 2013 with 8GB of RAM doesn’t go above 60%.
You have a TVS-872XT with a Core i5-8400T and 16 gigs. Something seems wrong if yours is being crushed.
Do you feel like power cycling the NAS before bed and grabbing some server logs in the morning?
What else is your NAS responsible for doing?
EDIT: I also found a good forum post for speeding these tasks: Script to regenerate video previews multi threaded?
