The heavy oil trailer you have to transport to the drill site in smithville dam was sunk threw the ground when i got there, and cant be moved by wintch or crane. You also cant reset the mission because it says something is in the way of the trailer spawn, but its the stuck heavy oil trailer

Do you mean the "Construction Rig Semi-Trailer" which you need to pick up in "Drummond Island"? If so I have the same problem. The trailer is stuck in the ground and whilst the description of the mission states that you need a "High saddle", you can't connect to the semi-trailer while using a P16.