Random generated level with diffrent tiles size

Hello,
I made a simple blueprint that generate random levels from 10x10 tiles.

It works as intended but i want to expand it by making possible to spawn diffrent size of tiles that dont overlap with each other. I tried to to make exact same blueprint inside “procedural01” so if this tile get chosen by rng, blueprint inside of it will spawn four tiles 5x5 and place it instead of one bigger tile 10x10 but it dosnt work properly. When I run simulation it generates empty spaces in places where four little tiles should appear and show lot of errors:

Is it possible to make it work in this way or i have to make everything inside of one level?

BP is too small to see properly.

When you get the none error, just click the link on the far right end, THAT IS the thing that is accessing nothingness. No matter how much you think it’s not - just look at it until you figure out what you did wrong…