Urup farp seems bugged, scav and I both dropped troops (tried mortar, RPG and Standard) and they wouldn't cap. We tried dropping them on the farp pad directly as well as near the towers (and waited a full minute before extracting).
Edit: Sounds like a lot of things cannot be capped. We tried Arhyz Farp and someone tried Merlot Farp Cherkessk sam site and could not cap them.
Edit2: After I stepped away Arhyz did eventually cap when I came back, so it may have taken a while. But the other sites I mentioned did not.