Yesterday, in EPiServer Commerce 9.22.0 we had our biggest product piGRIP, completely stop working in view mode. We're not sure how to reproduce this, but a guess is that an update from our PIM system which would upload a new Catalog.xml for Commerce to import got some kind of EPiServer cache corrupted.
Completely re-importing a full Catalog.xml did not solve the issue. Restarting the site did not solve the issue. The only solution was to remove the variant from EPiServer and then import it again through Catalog.xml.
When trying to access the view-mode of the variant a 404 would be returned (our custom one). In EPiServer edit mode the variant was working fine though.