Did you try;
Right click game in steam library, choose properties, go to 'Installed files' and do the file verification. Also, be sure (in the DLC's section) all your DLC are checked off / installed first before running the file verification.

and, if still the issue...

Try unsubscribing the mod(s) in question and then re-subscribe them again to see if it resolves any corruption with the mod files on your system.

Not sure why you would have this issue... I mean, if it was something to do with the DLC itself... more people should have encountered this... which doesn't seem like it's the case? File corruption is only thing I can think of, off top my head, which might be leading to this issue.