Cover Images Not Displaying When Background is Fixed

Since upgrading to 5.8 and GB11, pages built using Gutenberg, with Covers and fixed background, will not display the image. If you turn off “fixed background” the image will display again. This is mostly true but not completely. Some pages (25%) seem to work as expected.

If I rebuild the panel, using background images (instead of cover) with “fixed background” it seems to work fine. But before I go and rebuild 100 pages, I want to understand what is happening and why. My logic keeps screaming this is an issue with Covers in Gutenberg. Covers have slowly started causing more and more issues and workarounds with every upgrade it seems.