ProFIelds Repeater Matrix

[froot]

I'm building some sort of two dimensional repeater matrix for a template.

So I create a field of type repeater matrix named grid_level1 and add it to a template, let's call it repeater_template.

That field has a couple of repeater matrix types, but each one only has a field named grid_level2, which is also of type repeater matrix.

That grid_level2 has different repeater matrix types, each of which has a different field (body, images, …). 

Now here's the catch: I want the grid_level2 to also include grid_level1 among its repeater matrix types.

But if I do that, save it, and edit a page that is using the repeater_template, the site is caught in an infinite loop and I get a Oye… Fatal Error: Maximum execution time of 30 seconds exceeded  

Restricting the "item depth" to say 3 doesn't help either. 

What to do? What's my logic error?