I have recently been mining in both the over world and the nether and I have ran into the same issue twice. After breaking a lot of netherrack with an efficiency 4 netherite pick, I begin to suffocate when I walk into the section I just broke, but there aren't any blocks there. The same happens when using my efficiency 4 diamond shovel in the overworld. Something that may be connected to this is that when I try to put a block (cobblestone) in the same space I was "suffocating," the previous block (dirt, netherrack) spawns back in. My theory is that the block breaks client side but is too quickly broken to register server side. Just my theory, tho. The issue is fixed when placing a block to spawn in the previous block and breaking it with a slower tool/fists.