Blocks mysteriously disappearing in minecraft?

A couple weeks ago I built a mob farm based on Mumbo’s design, and it works great. Ground level is about y=70 and it’s up at around 120-140.

A few days ago, after I hadn’t been over to the farm in a while, I saw it in the distance and water was pouring out. About 5 blocks had disappeared from the walls, including 2 dispensers. The water also damaged the redstone.

Yesterday I fixed it up and re-synced the dispensers, and then left it alone again. My main base where I hang out is about about 100×100 blocks away, where I can see it in the fog. Today again there is water coming out from a missing block. What the heck is going on?

This is on a multiplayer server, though I am the only one on it lately (just me and 2 friends who don’t play much). The farm is made of polished andesite, diorite, and granite, so endermen can’t pick those up. It’s almost like creepers are spontaneously exploding inside even when I’m multiple chunks away. But there haven’t been any holes in the floors, just the walls.