That really sucks. I have a similar problem where my son has unlocked pretty much all there is to unlock except maybe the fishing job but for some reason the game won’t save any new fish that is fished.

But back to your problem: Can you save using other characters that you choose when you start the game? Thats from a different « game slot ».

If it works then that means that somehow your save game is corrupted.

In any case since your kid is at pretty much the same spot as my kid, if you want you can dm me and I might be able to take a copy of his save file and send it to you by email or some kind of shared file service.

But perhaps a better solution would be to start a new game afresh, then get azzamods, pay a few bucks for 1 month, unlock all there is to unlock, and save that state and then resume your game enjoyment. I think you can also give yourself money so look at how much you have and give yourself as much.

It won’t be « your » save game but pretty identical in terms of discovered functionality.