Updating Metadata renders NAS unusable

[ahasenfr]

I'm not really sure where to start.
My NAS is QNAP TS-673A with 16GB ECC RAM and 6x Seagate Exos X - X16 16TB in RAID6 configuration.
OS is QTS hero, so the file system is ZFS.

In general Jellyfin seems to be working fine.
But everytime I try to update metadata or just let the system search for faulty ones, the load on the discs is so high that I'm not able to do anything at the NAS.
The times before it just took really long and I was still able to get some data on the resource monitor.
But after starting a manual metadata update on sunday, I'm still not able to get to the resource monitor.
Only stopping Jellyfin via the app centre restore operability.

Not sure, maybe my Jellyfin is broken.
Because I had previously 01 on the machine just to test, then tried to update via the app center.
This was done wrong, maintainer showed me how to: #107 (reply in thread)
But only after I already uninstalled the manual installation of 01 and installation of 02 via app centre.
When running Jellyfin, the version displayed is still 01.

So I'm not quite sure if something with the installation is wrong or if the metadata update process is buggy....

Sorry, I'm new to all of this.