Sol System - Escort Convoy from Dublin problem

Have you your game fullly updated via launcher? I know for this mission was done updates.

But there is one basic rule when deal with such problem in SP: load last MISSION save anfor this mission: undock asap, form immediatelly on leader train (mission waypoint if I remember well) and not touch anything from that moment. When you jump, only enter formation again (leading train aka mission waypoint), and again don't touch anything. After is convoy attacked wait for command and after kill attackers quickly and again enter formation. This way worked for me.

p.s.: when something react like you described, then it mean only one thing: mission triggers were corrupted, mostly it happen when is used autosave. Using mission save should assure that all triggers are reset.

If all this will not work, please send me your last mission save, I can try pass this SP part and send you next save.

What Martind said is basically right, the main problem in this mission is : ........ WAITING

What I also sometimes encountered : due to the ... "abilities" of the AI-autopilot of the train it often seems unable to
"hit" the point, where it will be sucked in by the trade line.

Something that helped me - in this mission in general :
- before going into formation with the train after a jump gate jump steer into the proper position by yourself (at about
2 o'clock position), stop and THEN push formation button
- really, really WAIT for the command to attack the pirates (Hessian fighters)
- THEN again form with the train AFTER you returned to the position mentioned above. The train is then - most of the times -
in a better position in relation to the trade line
- WAAAIIIT
- or : when you leave formation the train also stops. This - sometimes - when the AI-pilot is seems just "circling" around the
trade line beacon "helps" after reentering the formation the AI-pilot to realign its train while going on a slower pace.

But in the first place : follow the orders of the mission BY THE LETTERS, if it takes longer, well : have a break, go to the loo .....