I was zooming around in creative, checking out my old world on the new snapshot, and there was a lot of weird stuff happening.
I started out in the nether because that's where I was working last, and one of my nether portals was completely down, and the other one was up, but a block was missing? It makes no sense and i hadn't gotten a chance to take a snap shot, but the portal was doing the swirly nonsense, but a block of purple swirls was missing in the bottom right corner.
Then I was through a plains biome with some tall mushroom trees with mooshrooms and what not, and the space in front of me kept going blue like the sky as if it wasn't rendering, but the blocks further out were already rendered. (picture attached.)
I then went and visited the base I used to live at in a jungle biome (there's a lot of ladders) and while I was trying to get up into the second level of my tree house, I was stuck on the ladder, repeatedly and quickly, going up and down this ladder. I couldn't make a GIF unfortunately for you to see, but it has never happened to me before. It's like I was lagging on the ladder. (Picture also attached.)
Stone pressure plates are seem laggy and takes about 4-6 secs for the door to open instead of automatically in Nether.
In new spruce boat, looks as though the boat is filling with water when in it/ and when in water without being in it. (Picture attached.)
A lot of render issues in general.
Hope this helps! Other than that awesome!