At first I thought this was an indexing issue because I first saw it a few days ago when re-indexing Sangin (it says "index" in the error) when sticking the new index in my Project OPFOR mission.

But I saw this again last night using regular ALiVE and a regular index so I think you're right that's it's Project OPFOR or maybe RHS. I did some unrelated vanilla testing on Sangin and Clafghan and don't ever see this error.