I am having this problem even just on my own facebook wall. The problem is not necessarily IP addresses or accounts, it seems to be mostly the content. I believe it is specifically the content of the image, at least in my case. I often share links with sexual themes on facebook, though they are very far from pornographic. Lately, a link share on my own wall where the image is a female posing in a bikini on the beach seems to get flagged immediately after sharing and either gets deleted or goes invisible to the public. I am currently testing the limits of facebook's spam filter extensively to see what does and does not pass as spam to facebook.
If anyone would like to work together on testing the spam filter, please PM me or reply. There is a lot of work and resources to be done until I can get it right.