Ask to buy causing apps to crash

Since the new iOS update, I activated the Ask to Buy service on my son’s iPad because some of his favourite apps had increased age ratings he could no longer access.

I receive the Ask to Buy messages. This seems to work fine. However, now while my son is using these apps they will crash/kick him out with no warning. The app icons for these games then disappear for a few minutes from his screen preventing him from restarting his games immediately.

This is causing a lot of frustration. We’ve tried restarting devices etc. our devices are fully updated. I have no idea what to do.