Edit: I think AngeGallego's fix only fixes the difficulty issue and not the ring issue.
I think it fixed none of both. And from my understanding the ring issue wasn't a ring issue, means
after flushing the mem pool problem still excists, but i'am not a coder, just some basic understanding,
but that's what i get out.
I think the problem is way deeper and more complex having mind some monero features have been
removed and others added and i bet there somewhere lies the problem with some kind of incompatiblity....
Just only a guess of course.