HoloLens - Camera object as child of MixedRealityCamera results in deviation

Hi!
I'm currently developing an app for the HoloLens which requires the use of a special Camera object with a specific culling mask. I made it a child of the default MixedRealityCamera so that it follows its movement.
Although it seems to work at first, the more the user moves and rotates their head in the scene, the more that child camera's vision gets deviated.
I put it as a child of the MixedRealityCameraParent instead and it works perfectly now, but I'm still interested: is there any reason it didn't work as a child of the MixedRealityCamera?

Thank you in advance.