I have this same effect in a new location I sometimes play from. In 95% of cases the game ends visually as described, without going through the end-of-game screen. This only happens when the game ends according to the game rules; if I resign, I do get the end-of-game screen.
This new location is behind a small business router, so maybe some connections from the outside do not get routed through.
I'd like to point out that the game has ended from the point of view of the servers. The one rated game I played from there ended as described (no end-of-game screen), but was tabulated as a victory for me, so it can't have been a disconnect or something similar. It is still an inconvenience, because the end-of-game screen does contain useful information.