Have you checked the float valve spring pins for movement and equal pressure when depressed?
springs all work. Don't know how to measure equality. They all seem about the same.
They probably are the same then.
I went back and looked at your set up. The picture omits any leveling device indicator. So, just a reminder that leveling is very important if you are not running the sight tubes right up against the bowls.
I observe rather large clear tubes. Any particular reason for that?
Then I looked at the fuel supply bottle, and wondered if there was enough volume to fill both the bowls and the large tubing. The longer the tubing run, the more fluid will be necessary to fill it AND all the bowls equally.
I would use actual gasoline, rather than kerosene. There is a density difference and the floats won't float at the same level as gasoline. I'm not sure how much level difference that would make. I just know the numbers are different.
Have you noticed any unusual spatial anomalies near your test site? Floating trees or somesuch? Just joking.
I'm probably watching too much Sci-Fi.
Cheers,