See https://en.wikipedia.org/w/index.php?title=Deprescribing&diff=760311175&oldid=760308049 Even if I'm editing with the intention of shortening an article (and in this case, I wasn't), it is rare that my copyedits actually reduce the page size, so the 20% reduction to the page size was a clear indication of problems.
It's easy to identify the three named sources that were deleted; I fixed them here: https://en.wikipedia.org/w/index.php?title=Deprescribing&diff=760312095&oldid=760311175 Note that I also re-added several re-uses of those; the bullet list at the end of the article contains six items, and each item was followed by a re-used citation when I clicked the Save button – but not when the page was saved.
But the page had 20 sources when I started, and now only has 16, and I'm not sure what else got lost.
Bottom line: It should be possible to copyedit an average article without VisualEditor randomly removing sources.