cj

plz help me with this I don't want my moms earned money to go to waste.

I did have it in my own world. I had a simple setup with a 2 hopper clock (see https://youtu.be/bYwzd62cLSw?t=1m5s), and the pistons and redstone didn't visually update. The piston sounds did play regularly, as expected and according to the clock's speed, so it really only effects rendering.

The render distance was set to 32 when this occurred, and as a workaround I turned the render distance down to 16 chunks, which seemed to fix it for me, as well as looking down.

This is very noticable with a large render distance. I had a piston running on a clock, which often didn't update at all for a few seconds.

(Warning: pure speculation below)
I think it's got something to do with Dinnerbone moving local chunk rendering to a seperate thread along with all the other chunks, which is likely to not be noticable when only a few chunks have to be rendered (i.e. when looking down), as the chunk-render thread would finish its work before the frame is rendered. however, if the workload increases, the thread might not be able to finish its work in time.

Farmland has a full 1 by 1 by 1 hitbox, and you don't sink away in it like you do on paths, hence the difference. Stairs, slabs and other non-full blocks show the same behaviour as paths.

Also affects path blocks

This is intended behavior caused by the slightly smaller hitbox of path blocks. Your Y level is 66.94. That means your feet are inside of the 1 by 1 by 1 block space of the path blocks if you're standing on it, and the light level inside an opaque block is always 0. This has no effect on mob spawning or rendering.

Dupe of MC-86921

This is introduced in this weeks snapshot and definitely not the behaviour seen in 1.8.8 or previous snapshots, not a dupe.