Error Vertex File

Error Vertex File for 'weapons\w_wst_ak47.mdl' checksum 912833314 should be 1652093399

Does anyone know how to fix that?

It means the file has somehow been modified from the original version.
Try re-downloading Counter Strike Source? If I’m not mistaken, that’s where that file comes from.

I have CS:S content on my server, but I don’t use CS:S weapons, because I have M9K weapons installed on my server.
I did not replace any files after installing M9K, and afrer 7-9 days I have that problem.