Really bad cubase performance after PC Restore

I have a big performance problem after a PC restore.
I am using cuabse 10.0.6 pro
My workstation has an i9-10920x CPU @3.5GHz with 24 logical units.
The system runs on a m2 and the data on a SSD storage.
I had to restore my PC from a backup (Veeam Agent Backup).
Now I have big performance problems with “old” projects.
Before the restore I was working with 256 or 512 samples.
Now the sound hangs even at 1024 or 2048 samples.
Cubase shows an average load of 100%. The CPU load is 7-8% at the same time. RAM is about 20%.
The Cubase peak load is very low. Cubase disk low near to zero.
On one project I turned off all tracks, the average load was still at 100%.

I have already repaired Cubase with windows apps and installed the update.
I deleted the vst xml under C:\Users%username%\AppData\Roaming\Steinberg\Cubase 10_64\Cubase Pro VST3 cache and rescanned the plugins.

I also cleaned up my Waves plugins and reinstalled them.
I have also made a backup of the project from Cubase and tried it with that. The error is the same.
the drivers of the audio interface are up to date.
i have deleted/renamed the .csh file und changed die filepath…

When I create a new project with 99 audio tracks and load 5 Waves and other plugins in each track, the average load only stays at about 50%.
Is there a way to clear some kind of cache in the project, or is this another error?

Cheers and thanks from Switzerland