When you copy a link from FB it often has a mass of gibberish starting with "fbclid=". Does that relate to what you're talking about? I always remove it when pasting.

I found a scary example of FB censoring URLs yesterday. Look at this:

https://mainlymacro.blogspot.com/

It's an economics blog, mainly about what's wrong with the Johnson junta's policies. The author is a professor emeritus from Oxford. Try to post that URL on FB and it will fail because it "violates their community standards". it appears that they equate criticizing Rishi Sunak with kiddie porn.