when I jumped directly on farmland, I started "block glitching" (I couldn't move, I was constantly teleporting to the same place). To reproduce, simply stand directly over farmland, and trample it back to dirt. I think it might have to do something with the fact that farmland's hitbox dimensions are smaller.
Environment
Windows 10, Dell Inspiron 15, Java 1.7.0_80
Duplicate of MC-104259