There is a bug in the game, an infuriating one that has got me, at the moment, stumped. It has to do with the system the game is using to keep track of cells that potentially need updating. In one specific circumstance, that being when fluids hit the edge of a platform and flow down off the side, some of it is often refusing to remain mark active long enough for all the fluid to flow off the ledge; it just pools up there, unsupported. If something happens next to it it causes it to "wake up" long enough for some more of it to flow away, but only for one frame.
I'll figure it out eventually. Just wanted to expose you all to my current personal hell.