jeff said i should measure current through each of the legs and make sure they are not more than 5-10% off max. if so you can change the capacitor to try and balance it or something- id have to research but i have a good clamp on meter to check easy.
if the 12$ can doesn't fix it, i wouldn't be opposed to getting a 7.5 or 10hp unit. When my 4hp drill press is in low gear the start up current pisses the phase converter off and one of the contactors clicks a lot till it gets going lol