On the official Netherfield Nottingham Network route clicking the screenshot button appears to take a screenshot, but if I actually go to My Pictures the file created is corrupt and cannot be opened. On the user-made route Glorious Devon clicking the screenshot button freezes the game slightly as taking a screenshot normally does, but no camera shutter sound effect is played and no file is created. Taking screenshots on other routes works fine, and I have checked this today.
Of course it shouldn't happen, but for the workaround part. Does Steam save your screenshots properly, which is by default the F12 key? (There is also an option for an uncompressed copy, if you want to edit or otherwise care about quality and want to use a higher fidelity format.)
