I agree with the water!! I had the same issue a few years back, I drained the whole tank and used a rag to dry it out good, you should have seen the stuff I found in there!
You have to make sure all is clean to start!! And this new gas loves water!! So a good water separator is a must!! I use a Racor with a clear bowl and drain so I can see the water and drain it.
A new ball will also take away from the guessing game, but make sure to get a good one! I have got junk ones right out the box when you buy them junk no name ones.