GSX is not failing or forgetting to "close" the editor, since if it really did that, it should always happen, in any situation, to everybody.
What really seems to be happening, if you don't see the quick edit dots being removed, is Simconnect just not accepting commands from GSX anymore, and this seem to be related to the total number of object in the scene.
I managed to reproduce this by going to an airport with lots of individual objects ( default EGLL ), and turning on FSLT traffic injection OR even plain FSLT traffic with no injection, and in some cases, GSX couldn't even create its own Traffic Cones, and this without *ANY* error logged anywhere, neither in GSX nor in the DevMode Console.
The only indication something was wrong, was in the "Simobjects" menu option of the DevMode, where you can see all Simobjects that have been created, and the missing ones are labeled as "Invalid", as if the sim reached the maximum number of objects, so it started to refuse to either ADD but even REMOVE existing ones, that's why you still see the QuickEdit dots.