Tropical/Swamp map tileset mod comes with its own integrated ambient sounds. Try renaming 'sounds_gc' file in 'Xenonauts\assets\mods\Tropical and Swamp Tileset' folder to something else, and see if that fixes the issue. Note that this will disable the ambient and map-specific sounds for the Tropical and Swamp maps, but should be a small price to pay compared to freezes and crashes!