Thanks @brian, @piac, and @chris12 ,
Contrary to what I wrote earlier, I now think that the update fixed the memory leak completely.
When I’m testing the file with optimization (i.e., the definition is recalculated at every iteration) I don’t see a memory increase anymore.
I still see an increase in the test file, but that is because it calculates all the instances at once.
(I removed the optimization to make it easier to share and use, but actually this leads to misleading results.)
In other words, with the memory leak, recalculations don’t make a difference, but without they do, which is as it should be. There might still be issues with large files, but my original problem is solved.