This continues to be a problem. I have recently started having this issue as well despite switching between Chrome, Firefox, Safari, and Edge. Had a chat with a tech support person and they couldn't reproduce the problem on their end but that seems to be because it takes a few minutes for it to manifest.
Clearing the cache helps momentarily. However, when editing I have to clear the cache multiple times per session. As this is a recurring issue Squarespace really needs to resolve this issue and I'd be willing to assist troubleshooting in any way possible.