The actual problem is that each collection allocates full memory specified in the game.project.
I created a project with hundreds of collections that are created through a proxy.
These are empty collections.
I took the project settings the same as the working project.
In other words, 27 empty collections required 133 MB of memory! This is the problem.
We need to control the amount of memory allocated to the entities within the collection.
For a large collection, we really need more than 4000, but for small ones 20 would suffice.