very slow map loading times

This is normal.
The game could freeze while loading a level, especially on the bigger ones.
The game is actually not frozen though, and is still loading things in background.
Don't touch / click anything, to prevent Windows trying to close the program. The game will resume on its own.

If you are trying to load a level mod for the first time since an update, it will take a bit longer since it's also generating new cache for it.
How long a level takes depends from the level itself (some levels have more stuff to be loaded than others) and how fast your PC is.

Said that, we are aware that in certain occasions loading times are long, and are working on it.