I'm making a tree farm in multiplayer and it's 150 blocks up in the sky. I water up to get some wood and find that I'm constantly right clicking the water source with my bucket and not getting a water bucket, but even so, the water flow stops. 

How to recreate:

Build a large tower (I would recommend at least 50 blocks)

Water up and you should find that every now and then you won't receive the water.