No Combine NPC Sounds anymore

Okay, so first hello all.

I will explain my problem as precise as possible. It’s been a long time I got Garry’s mod now, and I was always playing with the NPCs, especially the Combine ones.
All Combine sounds always worked fine until… I’d say a week ago now. I just started a singleplayer gamemode, spawned a Metrocop, and when I shot at him, no pain sound. I shot more, no sound at all. I finally killed him, and at my surprise, not any classical Beeeep sound, nor radio chatter. I tried with: Metropolice, Combine Soldier, Combine Prison Soldier, Combine Elite. Not one of them has the sounds working.
So, I checked in my console and this is the kind of error I get:
“No such sentence group METROPOLICE_DIE” “No such sentence group COMBINE_DIE” “No such sentence group METROPOLICE_PAIN” . I won’t list them all, but yes, it always begin with “No such sentence group”.

I want to precise that I only have this problem with Combine NPCs, the other ones (citizen, rebel, Alyx, Barney, etc…) have their pain and death sound (except the error with “missing token”, but I heard I’m not alone to have this problem). I also want to precise that they worked fine before, but it’s been a long time I didn’t test my NPCs, so I can’t tell you precisely at which day it suddenly changed.
I already checked:
-Addons, I removed them all from my directory, started Gmod and tested: sounds still don’t work, same error message.
-Searched in my hl2 folder, the NPC sounds are here, there are not any missing.

So yes, this is very frustating, since I really like playing with the NPCs, doing some street wars, but without their sounds, Combine aren’t the same at all. My last solution would be reinstalling Garry’s Mod, but I have a very slow connection (It took me like 24 hours to install Gmod), so I want to know your comments before doing this last and decisive action.

Thank you for your support.

This is an issue once again with missing scene files. It’s been reported, but at the moment, Garry is working on rust. No idea when it’s gonna be fixed.

Okay, thank you for your answer. I was also thinking there was a link with this problem and the missing scene files, but I wasn’t sure because I have never found my issue on other threads. I guess it’s a very rare issue. Anyway, thank you for your answer and now, let’s wait for Garry to fix it one day.