@nbianca this was very hard to isolate but I have a 100% consistent repro.
Make a post with the text:
hello world 123 hello world
Make sure there is a trailing space after the final world word.
Type in world SPACE
Then quickly try to edit your post adding a few letters to the end.
Something about our internal logic is “stripping” trailing and leading spaces and then tripping up the algorithm that detects that a post changed.