Grym Ore Cart Stuck

truckula

I have encountered this a few times, and have had a few other reports of it as well. I or others will go up to the mine cart in the final sequence of grym and it will not move out, thus preventing the turning in of fire elements. (Last time i was left with 50+ in my bag). Both trains are sitting there not moving. I have tried turning in both solo and in a 5 person party.