This is known but no solution yet.
I just found out that each frame of a GUI item get rendered 78 times. Than this multiplied by the frame rate of the movie gives the count of render action per second… It’s to much CPU load.
So CPU goes from 3% to 15% as example. It’s a bad GUI rendering system bit optimized for low power systems. On like a x86 CPU you don’t have issues because of enough power.
This “issue” will be a big, long process to solve…