Turns out the doors are baked into the bsp file and conflicting with the doors in the vanilla game. If there was a way to remove the doors from the bsp file... (This also suggests that the map is older than it looks, possibly made before the HL2 doors were added to vanilla Gmod)

I have the same problem, but it looks like there's no hope for me with a discussion this old.

me 2 help pls!

It's very likely that support for the map has been cut completely. Also I forgot to thank weemeiser when he gave his 2 cents on this. That would make complete sense in retrospect.

on a side note, restarting my game usually fixes this issue.

Downloading this addon might resolve your problem, it did for me at least.
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=104530717

Thanks! Although the problem went away by itself a couple months after I made this post for some reason.

For me I had to install Half-life 2 as well as Episode 1 & 2 to fix this