HL:Opposing Force has many bugs, first of all, the game softlocks at the intro/beginning. Second of all, the zombie marine throwing the scientist through the window is supposed to chase you, third of all the guard, that is supposed to kill the zombie scientist at the bottom of the stairs, is already dead. And last of all; the walker, that can't move anywhere due to it being cornered in by boxes, is straight up gone.
Edit: Nevertheless, it's a great port, but I can't figure out how to upload custom HL files, I tried uploading CL: Anniversary but it doesn't load the zip file. Any ideas on how to fix this?