I have consistent repro on at least 4 different discourse sites that I’ve updated recently.
Anytime I’d create a new post and immediately try to edit it to fix a typo or to add more text, it’ll start showing a warning in the bottom right of the composer window saying edit conflict with my own profile picture.
When I save the first time, it shows a popup saying the post can’t be saved as it is edited by another user but then it gives me the overwrite button. on clicking which, the post is saved properly.
I have another fix in the works which in my tests resolves the problem when you post something (that usually contains whitespaces in the end) and then you try to quickly edit that.