Try disabling "Autosave on transitions" from options, that should help.
It may not be antivirus, but something is interfering with autosaving. Maybe Styg can tell you more. Do you have any issues with quicksaving?
Thank you, the first bit does appear to be a temporary fix, and Quicksaving does work fine, oddly enough.
Notably, if you turn the autosave off, then turn it on after the elevator, the problem starts up again, so the problem is bigger than the first area.
Some more information regarding the issue: the game does manage to create two autosaves at the beginning, one for the tutorial and a second for the start in your room.
Attempting to load either of these saves causes the game to hang up on a black screen. No crash, just a black screen with the music in the background forever.
They also cannot be deleted without going into the program file and manually removing the saves.