Microprofiler Help

My game is getting random lag spikes and I am unsure what the related processes in the microprofiler actually mean.

I am assuming the lag issues are related to “Rebuild Z-order List” and “Layout” and that they are related to GUI elements? This is confusing to me because the UI in my game is VERY basic and doesn’t even have tween effects on them.

Here is the frame compared to a “normal” frame.

I would also like to note that from the time the FPS drops to the time it recovers, nothing in the game happens. No map changing, no teleporting, just basic scripts running.

-- bumping this because this unanswered forum post from 3 years ago is literally the only google search result for “rebuild z-order list” and it would be nice to have answers on how to prevent this from causing lag spikes