Unreal Engine 4.16 Bug Report (UMG Widget)

Nested Widgets not responding to id (z-order) change.
buttons added as a child object

Hello again!!! Finally I found the core of the problem (Bug). Now I’m unable to use can Cache on Invalidation Box. Any widget handled by Invalidation Box stop functioning. (passing-receiving variables, running functions et cetera).

Developer please reconsider your changes made to Invalidation Box. Can Cache functionality are extremely needed for mobile devices to be able creating a large number of child dynamically generated objects (buttons et cetera). I’m unable to move my project to Unreal Engine 4.16 without this functionality. I will lose about 50% FPS on mobile devices.