After doing some additional experimentation with demos in vanilla Doom 3, it appears they had their share of issues even when the game came out. Fixing the additional issue of crashes for PD3 when playing demos may not be worth it (assuming it's even possible).
Additionally, I ran into a bug that I thought was just confined to the "more monsters" addon; in Administration, there's a part where you cross over a room where Swann and Campbell are working on a computer. After some dialogue, the two run out of the room through a door. However, when I played through this level, Campbell ran to the door and then ran around in circles.
EDIT: I did not have the "More Monsters" addon installed when this happened on my current playthrough.
Also, I reinstalled PD3 and tried going through the weapon melees again. This time, all of them worked without any game shutdowns.
Doomblade3890
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