Random suffocating in nether with no clear cause

While walking around and digging in nether, every once in a while I will come across a block where I will start suffocating and take damage but with no clear cause. Will only happen if you stand on a specific part of the block ( around 1 pixel wide) . Cannot find a pattern. Seems to be very rare and very random. If you break surrounding blocks the problem goes away. Surrounding blocks are the basic nether blocks.