I had someone else on our team take a look and this is something that they found which hopefully is helpful:
“I can see the HTML is actually different between the working version and the broken version
The working version has a lot of utility classes that don’t mean anything to me “mjm-3q mjm-3r mjm-3s mjm-3t” BUT it is those utility classes that get the CSS to where it needs to go. The styles seem to be in there, but they aren’t being engaged because they are cascading from some of those utility classes.
The HTML is present in the raw source, not added with javascript, so this looks like a server issue, and the way it sort of hangs out and then disappears makes it looks like a transient server issue which gets cached first broken then fixed.”