Hi DCAT, I know how frustrating this is especially when one child can play and the other can’t. You’ve already tried the usual fixes.
Clear Minecraft cache and reset the app, update your graphics drivers make sure Xbox services are running and if nothing works back up your worlds and reinstall the game from the Microsoft Store.
Have you noticed if the freeze happens before the Mojang logo disappears or after the loading bar shows Syncing user data?
Best regard
Lucky