I am sorry but it seems I was wrong about the issue.
I think that the root of the problem is the pathfinder behaviour which has as obstacle a tilemap with the solid behaviour.
Here is how it looks: (the gray row in the taskbar is the preview tab)
The idea is that whenever Find Path is invoked the memory usage spikes a few mb's depending on the path length.
It is a bad practice to use pathfinder and tilemap like this or is there another problem?
Later Edit: I have managed to reproduce this issue on the pathfinding examples so I guess the tilemap is not the problem (?)
From what I've tested this does happen on Mozilla and IEdge aswell.