Hello @Wise Don't worry. You've already reported a lot of real/critical issues. So, it's not a problem if one of them wasn't a core issue.

I found what was causing the problem, but can't figure out why. No JavaScript errors at all.

I had deal with similar situations. In my case JS code, which is attached to the results of dynamically loaded content as text, had an error. But it wasn't shown in console. I suppose because of it was attached as text.

It's great that you've found the problem!