I have an issue that seems to occur in Safari in particular, both on the Mac and the iPad. I don’t know whether the theme (GeneratePress Marketer) or Gutenberg is to blame, but have found no mention of it in a search for Gutenberg-related bugs.
What happens is that I load a page, and the caption for a picture appears overlapping the text in the block below it. If I reload the page, it lays itself out properly.
The page is rendering in amphtml, incidentally, via the official Amp plugin, in case that is another possible cause.
Has anyone else encountered this?