Found the solution to the issue by accident. One or more of my libraries were outdated/corrupted (not sure which, moxy didn't say), did a system update and restart. Now it works.
I have a strange error that I never had before.
I can set a brush to a function static and make a perfectly standard door. But if I try to make a brush into a sliding door (using either the premade default or modifying the parameters of a default door) then the door goes +X+Y+Z whenever it's opened. This doesn't change if the tranlation direction is set to a different value.
I've tried this on a couple different maps, I don't know what to make of it, and I have no clue about where to start.
Please help.
DarkRadiant 2.5.0x64
TDM 2.08
Description: Linux Mint 19.3 Tricia
5.4.0-56-generic #62~18.04.1-Ubuntu SMP Tue Nov 24 10:07:50 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Intel(R) Pentium(R) CPU G2020 @ 2.90GH