Serialization of list in list problem with depth

Hi there. I have a class of Object type which contains a list of the same class. Thats all good and show up in the inspector as intended, but after a certain depth (not that much), it seems, that the list field dont show anymore in the inspector (probably dont exist at all since I get a null reference exception at that point after a debug test to see if the list exists at all!)

Do you have any clues on that?

Thanks