From what I've been able to ascertain when working through the contracts, we move one trailer from the railway Station in By The Lake to the set near the Warehouse in Mountain Ridge where it is still located.
'The Movie Star' task asks us to move another trailer, again from the Railway Station, to the set by the lake. Yet again in the 'Way to Success' task we are asked to move the same trailer from the set by the lake to the set in the mountains behind the Orestoke signs.
Now, in 'A Finishing Touch' we are tasked, yet again, to move the same trailer back to the Ship Movie Set in By The Lake. This particular trailer is moved three (3) times when a third, unused trailer, is still sitting at the Railway Station. This contract cannot be completed until the trailer is readied for connection, or the third trailer is brought into play.
Therefore, no further progress can be made because the last Emberrow Pictures contact - viz 'A Freezing Adventure' is locked. Also the two final contracts, one in each of the other two companies are locked.

The movie star trailer contract chain has been reworked between PTS 25.0 and PTS 25.1. It now uses only one trailer, and there's one more left over with no function. To experience the chain properly you have to start a new save - I recommend doing an NG+ with everything unlocked for easier time.