The only problematic account I have encountered so far is [email protected] but I have not tested many. On attempting to follow, it just hangs on “request pending”. I have been able to reliably follow the account from mastodon (for example).

EDIT: this appears to be working now after some testing, I assume it was fixed in a previous bugfix update. The request was still pending until I unfollowed and refollowed however, so you might want to set something up to check and resolve similar issues. (it would really be nice if I had 1 or more reputation so I could post without having to wait 300 seconds :P)