family sharing passcode issues

My son was traveling with his dad a few weeks ago and asked for my passcode for screen time since it was a 4-hour time difference. I told him I didn't want him knowing mine, so I went in and changed it temporarily so he had access while he was out of town. At first I just tried turning off screentime, but it wasn't working on my end, even though it was showing up on mine. Since he's been back, I can't change his screentime passcode back, and the only one I can change is mine (which I've never even noticed being an option before, but probably because I've never had one on my own phone). It's like his phone is now the "parent" phone, even though it still shows me as the parent and I can get into his account and edit screentime, turn it on/off, set all the other limits, etc., but it won't let me change his passcode and the passcode that I changed it to doesn't work on his phone, but my old passcode does work on his phone, so even if I turn his phone off he can just turn it right back on. It's so frustrating. I have a 14 Plus. I had him update his phone last night and it's still the same.

[Re-Titled by Moderator]

Original Title: family sharing passcode issues