Its happened enough times that I think it’s a bug of some sort. I’m not sure what causes it except I think it happens more often when I’m making small changes and then hitting save. Then when I go to preview I realize my changes were not actually saved.
Another thing, I love the block editor but I don’t like how random code gets added around my custom html blocks. For example all of them get a blank
added around them and in some cases like with the <iframe> tag, it causes Publii to add a div with a post__iframe class that completely ruins the bootstrap ratio class I added around my iframe. In my opinion Publii should not be making changes to the content I added in the HTML block.