never had any similar problems with any of my 550-650 measures with a multitude of different powders,7625,titegroup,4227,trailboss,4759,4895. I use small measure slides for small charges and medium slides for rifle charges.
If, as you stated, you are getting some "double charge" sized charges, you have to be double-pumping the handle somewhere in the stroke. Mechanically impossible to get a double charge from a Dillon measure without a double pump.
For the light charges, static might be the problem but I doubt it. If your still getting irregular charges after a wipe down, watch the little square plastic thingy that operates the measure slide in the measure frame, if that doesn't travel the full distance in its track on each stroke then it needs adjusting ( the wing nut on the end of the operating rod). If it is traveling the correct distance then try adjusting your stroke speed to give the measure enough time to fill with powder.
The first commandment with any press that dispenses powder in its operation...one full, smooth stroke up...followed by one smooth full stroke down...every time. Not suggesting the op is not doing this, but if someone starting up with a new press can use the tip...