Hey Hans, being a developer I can tell you it would likely help the WUFI guys to have more details ... I have not experienced this myself yet.
So questions I would have
1) what is your graphics card and driver
2) What OS are you using
3) How did you create the model, was it done 100% in wufi or did you import it and if you imported it where did you import it from, what plugin version was that running, and what version of the software was it (like if it is sketchup Pro 2020 and the current wufiplus extension as an export)
4) If you created this model in a third party application for import can you link the exact file here as well as the export created from that software you used to import into WUFI (assuming you did)
5) Can you provide your WUFI files for review to see if others experience the same issue opening them?
6) What version of WUFI are you using.
This is likely where I, as a developer, would start to look at the issue seen here. The idea being the more information the WUFI people have the more likely they can reproduce your error which in tern means they will be able to fix it in a future release or patch
Hope all is well and this doesn't happen on all your models. If I were you I would import other peoples models and if they do the same thing then try WUFI on a different system all together.
Good luck!