yeh im having similar prob but i kinda solved it by putting path_corner at start and one at end of a corridor and tested it worked to my surprise but no sound obviously and i check console and says
SV_StartSound: ambience/loader_step1.wav not precached (0)
SV_StartSound: ambience/loader_hydra1.wav not precached (0)
SV_StartSound: ambience/loader_step1.wav not precached (0)
SV_StartSound: ambience/loader_hydra1.wav not precached
over and over so i have searched it but i cant seem to locate these sounds any idea where they are?