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On the /blog/add page when selecting an author, click on the add user link, close both open windows, and the custom fields section becomes open, click on it to close, but trying to open it again, it glitches closed right after that.
Screenshot links provided for stepbystep of what was done.
then it just glitches open->closed when clicked on. refreshing the page tempararily clears the issue. and going back to the add user link more than once, it rinses and repeats the glitch but adds an arrow icon each time until the page is refreshed.
If this was a bit too confusing I can try and explain it a bit more.