An error happens when you go from [insert board with yotsuba default] to /1ntr/ that changes the board default theme on /1ntr/ from Muon to yotsuba. You can fix the error by going to themes and switching around the 1ntr default until it is muon, but it should be muon automatically.
/qa/ - Questions and Answers
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Thanks for letting me know. Not sure why this happens and will look into it and fix.