Whenever I’m playing on a Realm or a Server, a common glitch I see is the Phantom Water and Lava glitch. Flowing Water/Lava sometimes generates without a source block, and sometimes it will just float in midair as if there was a barrier block under and around it.

Another thing that happens is that the flowing water/lava gets cut off before reaching 8 blocks. It also makes water and lava not react and not form stone, obsidian, or cobblestone. The glitch can be fixed ingame be updating the water/lava