Problems with the layer object

[kromblite]

I'm making an isometric platformer. In the game, everything has a collision box that's separate from its actual visual image. This is so I can make isometric platforms and other things to give the game some visual depth. I've been using the layer object's "sort by x" and "sort by y" feature to determine how the platforms overlap. Ideally, I'd like these platforms to overlap like this- ideal.png
Unfortunately, if a block is simultaneously above and to the left of another block, problems arise- real.png
This is because one block is simultaneously being told to overlap and be overlapped by the other block. Unfortunately, as far as I can tell, the layer object doesn't have enough flexibility for me to fix the problem. Is there a way to fix this? Or should I just stick to making normal platformers?

[DavidN]

Does the Select object have actions that could help you here? (I'm not sure about this, as I've never dealt with this problem myself). What order are you running the sort by X/Y actions in just now?

[kromblite]

Here are the events as displayed in the event list editor-
screenshot.png
I have a block type that's set to be invisible in its properties, and I've gotten an isometric block active to set its position to the block whenever it's overlapping the big grey rectangle (a detector I made to determine if a block is on the screen). More important is the layer object's event to sort the objects by X and Y.