I made a bamboo farm with a video guide by JC playz (youtube) on my realms account in the nether. This grows bamboo by moving sand back and forward with pistons. I have made one before with kelp using the same method  in the overworld with no issues except the machine breaks if you log out while its on. Today my realms account lost connection and when it reconnected there were sand blocks in and around the machine that could not be mined and you could walk straight through as though they were not there. Additionally these sand blocks flickered as though they were clearly a glitch.some appeared in other blocks. They could not be mined, nor could i mine the blocks that were sharing the same space. I had to mine beneath them and drop them into lava lakes. I assume they are still there. This happened twice today and was noticed on both xbox one and iphone. As i have used this same method before without this issues on the overworld I can only assume it is a problem with Realms, the nether or the new hotfix.