Symptom: NPCs are unable to pathfind, T-Pose or glitch with their animation.

First Fix:

1. Join your Server
2. From the server console use (if running any other map than ow_citadel)
3. Disconnect from your server
4. Properly shut down your server
5. Start your server again and check if the issue is resolved.
(Optional) 6. Keep restarting, for me it took two restarts until it worked

Second Fix:
1. Access your server console
2. Enter following command:
3. Use following command to change to each individual map:
4. Repeat from step 1. until you did that with all maps.

Map List:
ow_assaulted
ow_breach
ow_breached
ow_canals
ow_citadel
ow_crossroads
ow_whiteforest
owc_superfortress
owc_traverse

Third Fix (100% fix gurantee):
1. Shut down your Server
2. Go to Steamapps/Workshop/4000/2713876035/ in your file explorer
3. Open another file explorer instance and go to /steamapps/common/garrysmod/bin/
4. in garrysmod/bin/ find the gmad.exe
5. drag and drop temp.gma from the 2713876035 folder onto gmad.exe
6. in the 2713876035 folder you now have another folder called temp
7. upload the contents of temp directly to your gmod server via FTP or moving the files over in any other way
8. start your server

Do let me know if it worked for you or not. I won't reply or support every user so bare with me.