Could you explain this play on words for someone who doesn't know Japanese?

I'm guessing but 誤解 => 'go kai', which means 'misunderstanding'. That sounds like 五回 => 'go kai', which means five times.

In Japanese, you often encounter words/phrases that sound more or less the same but are written differently.

Both the original Japanese (meaning 5 times) and possibly pun Japanese (meaning misunderstanding) are read as 'gokai'.

I don't really get how that pun works (it's not as though that's a common phrase). It seems more likely that it's chosen just because five is a round number.

If we're just going for homophones it could just as easily be "fifth floor" but that also doesn't make a lot of sense as a pun.