While doing some seed searching, I entered the seed "ramen" (108279111), /located the nearest stronghold, and found this. A fossil had generated into the portal room, but even more so into the portal frame. After many recreates of the world, this happened two more times. It seems that the fossil always generates in the back left corner, sometimes outside of the room. My guess is the fossil generates after the stronghold causing this problem.

This is the same as MCPE-40017, where it says the issue was resolved as "not fixed." But that is for the bedrock version. I have not tested to see how far back this is possible, presumably in 1.10 when fossils were added.