[Help] Marksmen DLC - Not running unless ran as a mod

I have an odd issue - the Marksmen DLC will not launch with my game unless I run it as a mod (-mod=Mark).

All other BI DLC (Karts, Heli, Zeus) run fine.

I've tried verifying the integrity of my game cache - no invalid files found, but game still won't launch with the DLC.

Has anyone else experienced this problem? Running the Marksmen DLC as a mod each time is not possible with my community (we use fixed PwS repos).

Thanks.