Bad performance in Windows 11 23H2 under Parallels 20 & 26 with August cumulative update

I still use Windows 11 23 H2 as virtual machine because 3D performance is better than with 24H2.
However with the Cumulative windows update from august, the performance in Passmark Performance test 11.1 drops significantly from 8850 to 5160!
2D graphics are down from 1385 to 682!
How can we solve this problem? I had to uninstall the Cumulative Windows 11 update from august.