I think FB is just changing their advertising algorithm from time to time. Their programmers seem to deploy their new attempts to the users, so we can find their issues instead of using internal testing.
I don't think or talk the same way as the owners of FB, ergo, I land in FB jail on a regular basis. So, the ONLY thing I use it for is browsing Marketplace to see if I can find a decent price on a piece of equipment or gadget that I want. Now and again, it happens.