Hi guys,
I’m also recently having the same issue as @emilyluxton in that posts seems to be randomly saving incorrectly and reverting back to an old permalink. I do suspect it is happening more with “older” posts (ones published in 2016, 2017, 2018) rather than newly published posts.
I do use a plugin called https://www.ads-software.com/plugins/revisionize/, which I know is not totally “up-to-date” yet always seemed to work fine before WordPress 5.5.
Sorry, not sure how much help I can be but please ask and I will see if I can assist!
Cheers
