i had a small area with falling water like show in picture.
this caused germs to increase at an extreme rate. its like the germs from the falling water was added to the lower, without being removed from the layer above, i ended up with like 500 million germs in the water, from some 400k germs at start. also, i did notice a heavy performance hit on my game as this occurred, the hit to game performance persisted after i fixed the waterfall.
this seems to tie in with problem i seen a lot before, where carbon dioxide is not displaced by heavier water. sometimes i even had a constant flow of water on tiles, interrupted by carbon dioxide which has lead to flooding. (this last was observed in AU, not seen yet in OU)
Steps to Reproduce
as in picture, germified water, 2 blocks high that tries to fall down on CO2 which refuses to be displaced.
This issue has not been confirmed by a developer yet.