The experimental build has changed how resources are split, after right clicking, you get a dialog that you have to confirm to perform the split.
The new UI is probably an improvement for most people, however it makes it really tedious to distribute biomass/fuel into generators:
Let's say I have 4 generators, I usually try to put the same amount of fuel into each of them so they will all run empty at the same time. In the "live" build, I can just right click on my 200 fuel, and then again right click again on the two 100 fuel stacks and have four 50 stacks. This takes a second.
In experimental, I have to move my mouse to the confirm button each time, making this process much more annoying. I'm not looking forward to having to fill 8 generators.
My suggestion is to add a preference toggle for both styles of splitting (or maybe activate it by holding ctrl+right click), so people like me can get their fast split, and others can get the more user friendly, but slower method