We found a bug in the layout editor which is annoying and that was introduced with this update: when using the component PAGEBEANCOMPONENT (which you use when embedding page bean components into a page), then the "t:pagebeancomponent" was excluded from loading the layout into the editor - and later on not saved as consequence.
So opening a layout containing PAGEBEANCOMPONENT and saving it removed the corresponding part of the layout-XML.
For this reason we just published 20211217.
To make sure: this bug is a tool-bug! (not a runtime-bug)