I have not seen this happen with shadows.
I would...
Check video drivers are up to date.
Check how much free RAM yo have.
Check how much free space you have on your local hard drive.
And make sure Archicad is up to date.
Barry.
One of the forum moderators.
Versions 6.5 to 27
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11