I got this same error from using the CUP Terrain - Core mod. Steam tends to corrupt big downloads and big mods are especially vulnerable to this transfer. When I checked the integrity of this mod I found that 5 files were corrupted. More info on their issue tracker: https://dev.cup-arma3.org/T2877#44819
Basically, download mods directly from the developers site and preferably via Torrent since it's less prone to cause corruption. That solved problems for me. I have also seen people re-install everything but that is a bit more nuclear.