I've never had any problems with the Outcast dread. Strange.
The only way to completely fix the issue would be to completely re design the docking system. For example, to create a new unlocking structure special for big ships, and place it above, below or far away from a planet.
(If you find any mistake in my English, please let me know via a PM)
(Really, I speak terrible English, so please, tell me if I make mistakes. I'd like to improve it a bit )