He doesn't know English very well so here is what he shared with me.
we tried a lot of things. We tried verifying the integrity of the game files, deleting mods, deleting and downloading the game again, etc. I asked whether his Windows 7 and the drivers were up-to-date he said yes. It may have something to do with the end of support for Windows 7. This started about 2-3 days ago. He was able to enter the game successfully with no problems before that and it ran ok as well. But this suddenly happened.
Here's the client log. It seems ok but it just cuts suddenly in the end.
I wasn't doing anything unusual when this started. He started telling this suddenly.