I don't share all my photos here with Facebook but some I think may be of interest to colleagues I do like to share. This evening, though, I've tried several times to share a particular photo but the thumbnail is always of another photo entirely. Usually not even the day before or after.
You can shift through the photos on the FB upload page. There is a little arrow next to the selected picture and it will move through the pictures til you get to the one you want. I have had that problem periodically for no rhyme or reason.
It's a quirk in the system. Sometimes I can't upload directly from my Mac. And, sometimes I can't share from my ipad because the thumbnail is wrong. There are times regionally with upload issues, but they ususally work themselves out. @jools
Anyone else having this problem?