stepper motor will not reverse in full step mode Ramps 1.4

I have built my own printer and extruder and everything works with the ramps 1.4 board and A4988 drivers when I put all the jumpers in for 1/16 micro stepping

when I take all the jumpers out for one driver and try to get the stepper to operate in full step mode: it will turn in one direction but not the other
when I try to get it to run in reverse it just sqeals and vibrates
seems to be putting out lots of torque in the direction that actually turns

anybody ever encounter this problem?
is it a driver problem or maybe jumpers?
I was going to try a new driver to see if that works but thought I'd post first
any suggestions appreciated...
cheers
Ian

Did you change any settings when you removed the jumpers.
If not motors will try to run 16 times faster which may screw up the timing of step and direction pins if its too fast.

no I didn't change other settings but the steps per MM were only about 300
but the stepper had no problem turning the one way with lots of torque and about 50rpm I'm guessing

I wanted to drive a geared head stepper and when I tried to make it run fast enough when microstepping it would do nothing but squeal a bit and not move