My EB installation has both blog posts I migrated from a previous blog as well as new blog posts I published directly in EB. The older posts don't have a cover image whereas the newer posts do.
Earlier this morning I upgraded EB to 5.1.5. After the update I noticed that, on both listings and entry view, the old posts were showing a cover photo. Of course this was just EB grabbing the first photo in the content to show it as a cover photo, which apparently was part of a change in EB 5 somewhere.
Fast forward a bit and I saw you released 5.1.6 and I saw in the changelog you were addressing this very issue. So, I updated to 5.1.6. I disabled the "first image as post cover" option and now both the older and newer posts look correct in the latest/listing view. But, when you go into the entry view, a cover photo still shows.
To be clear, I want the cover photo to show as expected when the post has an actual cover photo. But these older posts do not. Yet the first image in the content of these posts is being replicated as a cover on entry view. And, if I disable "show post image" in 'view' settings it disables all cover photos, which doesn't work either.
I've attached a screenshot which I hope provides a better description.