This problem has been getting worse and worse for my site.
About 50% of the content pages end up with a 'floating pile of likes' and when someone new Likes one of these pages, it shows the wrong URL on Facebook.
Sometimes if I change the URL by appending something on the end it clears up, sometimes when I use the Linter tool it clears up. Lately these things work less often than they used to.
This is ridiculous. I've read reports of this happening of the dev forum from over a year ago, and the issue never gets resolved. I know my users like the Like button, but they are so frustrated with and are sending me so many complaints about it, that I'm about ready to just remove the Like button altogether.
The dev forum for Facebook hasn't been any help to me, but I thought maybe someone here on WW might be able to help.
The only thing I've read about this, is that apparently the linter tool "should" clear facebooks cache and crawl your site properly to sort these kind of things out. Whether or not it works I cannot vouch, though I have shared the same problems as you.