Editor lags when coming out of play mode...?

So I'm doing some work with procedural mesh generation, and Unity doesn't seem to lag whatsoever in play mode (and takes almost no time to enter play mode, either), but every time I go to return to edit mode, it seems to take a really long time, sometimes freezing up indefinitely, until I end the process and start Unity up, again.

I'm getting no errors or warnings, and I don't think there's that much garbage collection that needs to be done, each time, but perhaps I'm wrong. The odd part is I've done far more memory-intensive stuff, in the past, and never had this issue.

Does anyone know if there's some sort of memory leak in procedural mesh generation, or mesh-combining that would come up when destroying a procedurally generated mesh?