Darn, I searched so thoroughly before posting. The repeat dragon eggs and end gates should count as new bugs, at least.
This is not a bug. The water was drained, and then began to flow again. Source blocks were created in the normal way water source blocks are, and the water eventually returned to normal. To avoid this mistake in the future, section off areas that you plan to drain so that water cannot create new source blocks in the area that you just emptied.
This is not a bug. The dragon is not stuck, he is perching on the portal. This is intentional, and part of the new dragon fight.
This happened to me once, occurred after a strange chunk issue. He had not appeared before that point and did not appear after I rejoined the world.
So this is a visual bug?