Image sequences incredibly slow on iMac Pro

AE 22.0.1 on iMac Pro with 12.0.1 Monterey, 64 GB RAM, image sequence stored on internal NVMe drive. 

Any image sequence (file type does not make any difference) is incredibly slow to play, up to 500ms Frame Time. This is totally unacceptable.

Tried, didn't fix:

- different image formats: TIFF, PNG, JPG, all 1080p

- resetting AE prefs

- rebooting

- reinstalling AE

- hardware acceleration on/off

- bit depth 8-32b

- moving the sequences to a different drive

Any clues?