losing steps

Hi All,
I am putting the finishing touches to my newly built router table,
and to my surprise, with the power on to the Y motor , I can make the
motor lose steps, when I put my shoulder into the cross slide.
Is this normal? the motor is a Pacific scientific 645 oz-in, and I am
using gecko G201a. and 1 rev of the motor is moving the cross
slide .8"
I know that the G201a halves its current when stopped, can this be
adjusted if necessary?
Colin