Turn wont proceed bug

[RightDeve]

He pushes them, confirms and game ignores that.

This I assume that the End Turn button does work at least initially to provide him with a confirmation screen (Y/N press). Then when he pushed the Y button the game appears to ignore the press of the correct button.

Maybe some keyboard problem. This is one of the most common problems found in notebooks or laptops, where you press this button but that character appears instead.