Cec, this is your file, just opened and directly rendered:
...as you said, no problem.
But zoomed in only a little bit:
... the problem reappears.
The biggest floor is a little bit displaced, so I tested if this can be the problem. But neither push it to the right position, nor delete the floor and rebuild it helps.
If you create a second level and then increase the original level by 1mm, you can see strange "rays" on the floors in the 3d view:
I suspect this has something to do with the problem, but I still can not figure out what exactly caused it.
----------------------------------------
Pascal
SH3D 6.6 / Ubuntu 22.04 (Mainline-Kernel) / Radeon RX580 / Ryzen 7 5800x
