I have one peculiar error to report - one that has been around on my forums since the beginning.
I've created a custom theme for my forums based on the persona theme, with only a couple small changes. Most of the graphical customization I have was added in Appearance -> Custom CSS and work for both my theme and the persona theme.
When I click on the Edit button to change my user profile - that is, I open this page:
the custom CSS (or at least most of it) is destroyed and the page ends up all messed up. I need to refresh it to make the CSS load properly. Once refreshed, the error won't happen again unless I close / reopen the browser.
That page is literally the only page on my forum where this error happens. Switching to the original persona theme doesn't fix the issue.