I've played with many kinds of servos. I second the idea that a 1-Amp supply isn't nearly
enough current for 12 servos, no matter that the fuse doesn't blow, or whatever else
you might think. Maybe the supply simply drops out momentarily, and the servo control
loops go bonkers. I also doubt that your USB port can supply enough current.
I always use 5-6 NiMH rechargeable AA-cells in series to power my walking robots, and
they will easily provide enough juice for 12 standard servos [44 oz-in]. Allow about 300-mA
for each standard servo, so the supply needs to be in the 4-Amp range. You need to know
how much current your particular servos draw, for starters.
Also, many servos go totally berserk, and run over to the mechanical stops, when the +V
voltage drops too low. Also, on many types, when you first apply power, the servo horns jerk
a bunch of degrees. My GWS servos will move over 90-180 degrees if I power them on/off a few
times. I don't know about your particular type. These issues have long been a problem with
walking robots.