This is often caused by mod threading, which does improved loading spead but can lead to these kind of issues.
Disable clicking on Menu->Configuration
On the GAME tab find the second option from the bottom (mod threading) and remove the check mark from the box.

If this does not help he should clear the local mod cache (best google for how to do this, as the cache location differes between mac and windows machines as well as personal settings).

I hope this helps.

Btw: I am notified about new comments but not discussions. If you have questions, commenst are probably the better option.
Alternatively you can usually reach me on the Tabletop warden, ASoIaF Wargamers or Northern Realms Gaming Discord servers, where you'll find a TTS / Online Development channel, where you can post questions like this.