Well, I have found out what happens, and so solved the problem. When one activates page-builder and calls up the siteorigin-editor, code is introduced though you do not see it when writing in the siteorigin-editor, neither in the text mode or the visual mode. However, if you return to the regular editor (leaving the page-builder) and you use text mode you can see the code, which appears mainly at the front end of the file.
The post looks fine when viewed on a blog page which has the default template. However, on a blog page using grid-and-masonry if the post uses the quote format, what appears in the masonry tile is the code that has been inserted in the front end of the file. Remove the code and everything works fine. Or, of course, don’t bother with page-builder while setting up a post having quote format.
Might be worthwhile having some note about this in the manual. I have other thoughts too about stuff missing from the manual.
