From my experiences:-
1 Rogue photos usually appear in the final submitted post, not in the post Edit window.
Recent exception: Rooky's HMS Amethyst post, a new phenomenon.
It seems to me to occur when two or more members all submit posts within a very small time frame. I can liken it to 'cross modulation interference' within multiple radio systems!🤔
Something I know well from naval ship comms systems.
This first cropped up several months ago when pics in one of JB's posts appeared in several posts in the same thread - but not in his own post! I spent some time putting the pics back where they belonged. Problem went away for several months but has recently cropped up again.
2. The phenomenon is not limited to Harbour posts.
3. It's not always the same photos.
Not like the case of the mysterious 'Fish Avatar' some time ago!
I've also noted the text deletion, as Rob describes, after selecting photos (or any other file type). Doesn't always happen but I have learned to copy the text just in case!
Hope this helps track it down.
Cheers, Doug 😎