This seems to happen to me after a save, and I've noticed it happen a couple different times now on different saved games. It's not reproducible, in that I'm not sure what makes it happen, but it is reproducible in that if I play a PreWarp game for a few hours, it always seems to happen sooner or later. I don't recall running into this before 1.9.5.5, but I've only been playing for a month or so.
Below is the screen shot filtering on Galaxy Priority. When I just tweak it to "...by Your Empire Priority", all possible mining solutions go away. I'm happy to save a game if that's an appropriate way to submit the problems, but I thought a screen shot might be more useful. I'll see if I can embed an "after" image in a second message.

