Hi. I had the same problem. For test purposes, I made a build of the Product Viewer Template back from 4.21 (now part of the Collab viewer template) without making any modification to it. Unfortunately I modified 2 settings for a second build, enabling Full Rebuild option in the Project Settings and switching from Development to Shipping, so I can’t really know right now which one has solved the problem, but now my build is working fine.
I’ll try to make a third build switching back to Developement, to find out which modification really solved my problem.