Unfortunately, I don’t think this is a memory leak. But if you want to share a sample project of your setup, I can double check. I have a few other projects I’ll be looking at this week.
You definitely got one with the terrain brushes. ie once you select a terrain gameobject, the terrain inspector loads all heightmaps of all brushes into memory. If you have a 100 in there, well, you know what happens. Any update when this will be fixed?