How much system and graphics memory does your PC have, and how much does GMod use when playing the map? The game may become unstable when you exceed your physical memory limits. If that's the case, try disabling other addons temporarily and see if that helps.

♥♥♥♥, just realized the author replied.

my laptop has 4GB of ram (the graphics card is pretty bad, so probably 1GB GDDR).

i was actually trying to see what addons are conflicting with the map. i partially managed to fix it. now the map crashes when you're going underground. there's a place on the map where the game just crashes. it's the research lab, i think.

anyway, sorry for replying so damn late

okay, i'll be getting a new pc soon. i'll update when i try the map on the new system