See https://en.wikivoyage.org/w/index.php?title=Wikivoyage:Joke_articles/Mars&diff=3454917&oldid=3454830

I have an ongoing but intermittent problem with editing in the 2017 wikitext editor at Wikivoyage. Sometimes saving actually does save the changes, but it looks like nothing happened. The Save dialog remains open, toolbar remains visible, and if I click on something else to navigate away from the page, I get an error message about there still be unsaved changes on the page.

In this case, I tried to save changes again, and it automagically resolved the "edit conflict", with the result that this new sentence was added twice. I don't know how to trigger it reliably, but it happens pretty much every day that I edit at Wikivoyage.