I thought this was specific to my site, but I even see this behavour on the demo page at https://piccard21.github.io/busy-load/
If you click on the FullScreen button, the content on the page moves slightly to the right while the spinner is showing, and when you hide it, the content moves back to the left.
I'm using Chrome Version 80.0.3987.132 (Official Build) (64-bit)
How do I prevent this behaviour for full screen ?