I've encountered a strange bug with the Algae diffusers. They require 7.6MG of Algae and even auto sweepers with more than enough algae beside it won't deliver. I have to deconstruct and then reconstruct in order to get it working. I've also encountered the same bug with Oxylite delivering to the solid fuel thrusters and solid oxidizer tanks. It's always the same amount every time. 7.6MG.
it's random. but it affected both of my diffusers at the same time.