I don't know about the OP, but my issue was that the stringing machine just wasn't robust enough to withstand the pressure of the mains.
Case in point, two days ago I strung a Babolat APD with 17g poly @ 50 lbs. Hoop compressed lengthwise by a full CM.
yesterday, I picked up a used Gamma 4000 crank machine. After getting it all cleaned up (still need to calibrate it), I cut those Babo strings out and re-strung it. Same strings, same tension. This time, the hoop only compressed by 1 mm.
IMO, it's not the stringer, it's the machine. I didn't do anything different, I just used a different machine.
And BTW, crank machines are AWESOME compared to dropweights. so much easier. The whole job only took me 45 minutes, and I was VERY slow, as I was still learning how to use this machine (never used a crank before). I'm thinking that once I get proficient at it, I could probably string a racquet in about 30 minutes or so.