Certain games download, install, then dissappear, then have to install again.

I've downloaded that Windows 11 Installer, but there is a big problem with that. When I open that app and confirm the UAC dialogue then window pops out and instantly dissappears.

In addition to Maxen's point, I would also add that the "Resume Installation" notification will appear not just when a game hasn't finished its ORIGINAL install, but also any time an update downloads for that game. When that happens, the installation will
not actually finish until the next time you play the game. (With the new way games install and update, any time there is an update, it overwrites the old files for the game, essentially "re-installing" a newer version over the old one.)

So, in your instance, if, for example, an update to a game downloaded, but you disconnected and went to the holiday home before playing that game again, if I'm not mistaken, the network connection is required to finish downloading and installing the update.
So, the installation could not finish when the game was inserted, because the console couldn't find the network to finish the installation.

Also, if a download was in-progress at the moment you disconnected, that could be another thing to cause that error. The console knew certain games were mid-update, and the installation could not resume until the network was present again.

Not certain if either of these scenarios match exactly, but some thoughts on what could have caused the issue for you!

If youre using power saver then it stops downloading when you turnit off

Change your setting to instant on

If it is shown as installed from the in game store then it will be there. You can always check your Download history to see if it completed or to download it again. Remember some maps are only available in certain playlists. Hope this helps.

That's odd, and just to cover the possibility.
Can you try connecting the console to a different screen? Or using a completely different HDMI cable?