What is the rated current on your machine? Voltage should not drop so drastically during welding, unless you are close to the maximum rated current. Since you say this is a recent problem something else must be to blame. I agree with other posters- it sounds like a grounding issue, or else a loose, dirty or worn terminal somewhere in your machine. Additionally, In my experience, Voltage and WFS suggestions from ANY manufacturer or salesman should be taken with a grain of salt. Forgive me If I sound pedantic here. As a professional welder, it's your responsibility alone to select your tools and use them properly. After all one does not ask a car manufacturer how to drive, one does not ask a scalpel salesman how to do surgery. Only an incompetent surgeon would ever do so. On steels > 3/16" in thickness you really want to be using the spray transfer mode (provided you are welding in the flat or horizontal position.) *Conservative* spray settings for 3/8" would be 550-600 ipm and 30-36 volts. Though, you could easily go higher than that if you want to increase your productivity. The settings you quote are in the middle of "short-circuit transfer" range on the wire feed dial. This is FAR too cold. On 3/8" material you should expect to find lack-of fusion and lack of penetration defects in your welds when using short-circuit transfer. (You're welcome to do some bend tests to prove my point. Irregardless of the process used, good welds should *bend* through the heat-affected zone. They should NOT easily fracture at the root without bending first. If they do, your welds lack fusion and/or penetration. Does your welding machine provide at least 300 amps of output? If not, then it is probably not capable of producing acceptable spray transfer. If this is the case I would advise you to not MIG weld greater than 1/8" thickness for liability reasons. Finally there is a general rule of thumb to use: If you can hold the arc in one spot on the metal without risking burn-through, then your welds are probably too cold. Your welds would probably benefit from increased weld energy. Hope this helps. good luck.