I was wondering, can replays be safely deleted directly from this folder rather than via the game (which it seems I can only delete one at a time and takes ages) without corrupting the game and/or the replay system?
Sitze seems not to be the problem. What I noticed is, that if you click on the camera symbol in-game to open the replay selection page, it took ages to open that up. I, too have hundreds of hours of gameplay and since I deleted all but the most recent replay files, that replay page shows up a lot quicker.