200 is definitely very slow accel for a servo and may have been an issue.
What kind of machine is it, size/ weight?
If you attach your latest xml I will have another look and see if anything jumps out as being wrong.
Still strange that one direction is fine but not the other, as mentioned earlier it almost sounds like a runaway situation that you would possibly get if the encoder was not being seen as the control would just keep increasing the voltage as it would be thinking the axis is not moving correctly.
Hood