Thank you again.
My doing “Empty cache and hard reload” in Chrome wasn’t enough – but deleting everything (i.e. cache and local and database storage, service workers and cookies) using chrome://settings/siteData?searchSubpage=suttacentral was enough to fix that.
So maybe the root problem is as mentioned above, i.e. the software’s not mangling its resource names with a version-related unique id, causing stale-cache problems, and/or expecting users to delete this kind of thing themselves.