Lol, no, no fix, well, not really. And I suggest you stay away from reporting anything to do with ai. They are broken, and it is a known fact (at least for me), but it so so incredibly hard to test. AI near planets never is a good idea, they bump into the planet and just stay stuck there.
To get rid of them, make yourself admin and use /destroy_entity on every trade guild ship. That will delete them, if you can select them and type it, that is. I don't know if it will fix the lag though.