I know this is a slightly old thread. However, figured I would post my fix. I was setting up a FARP with dynamic slots. When I placed the invisble FARP and then placed the vehicles for re-arm/re-fuel etc. I was getting the same error. After trying a few things, I realized that I may have put the invisible FARP too close to the vehicles and some other units placed there for candy. Moving the FARP from 15ft away to 50ft away from the closest object fixed my problem. I didn't have to jump through all of the hoops mentioned above. Might work for some!