Have you altered mbases.ini any? I've had a problem before with poorly defining factions on bases leading to tradelane crashes.

It has been a while since I have been dealig with issues alike.

From what I read here:
1. The problem is in your file(s).
2. If the game crashes when you dock a tradelane, than the most likely course is that there is something wrong with encounters that are triggered by entering the tradelane. Which might be a tradelane encounter, patrol path encounter or area encounter.
The fault may be in the encounter itself, the ship involved or the loadout.

Since you mentoined you already checked those it is likely that the error is not so obvious to see.
What I would do is:
1. Edit de Iw03.ini and comment out all the encounters. When I say comment them all out I mean all of them. Make sure to include the area encounters.
2. Next dock with the tradelane. If the problem is not longer there, you know then that the error origins from an encounter.
If the problem persists and you have really commented out all encounters then you know that the crash is not caused by encounters, ships or their loadouts.
3. Now continue to reactivate all encounters that are not near the tradelane involved. Use FL Explorer's map of the system to identify them. Don't reactivate area encounters that touch or cross the tradelane yet.
4. If everything is still okay reactivate the remaining encounters group by group or one by one, just as long as you do it systematically. At one point you will find the one that is causing the crash. If there are more than one faction using this encounter, leave one active and comment the others out.

Hope this helps.
See you in Sirius
Buck Danny