It is quite simple... I just click on "view 3D PCB" to update the 3D PCB because 2D and 3D are out of sync when I made changes to 2D PCB. (same happens if creating a new 3D PCB from 2D PCB by clicking "view 3D PCB" if 3D PCB does not exist)
Fusion then switches to 3D PCB, progress bar (right bottom corner) appears and never changes, after a while windows message "Program does not respond" appears.
CPU stays at around 6.25% load (i9 9900k, 8C/16T, 64GB). Thats it... nothing more happens.
See the screenshot. This design was affected by the milestone bug. Could it be, that this bug is still present in specific parts?
Taskmanager-Screenshot: Load nailed at around 6.25%, private bytes and working set is nailed too, after reaching that values.