I apologize for misreading the OP. Moving the up and down arrows should not result in a left or right action of the OTA.
Mike's reply above might be a different issue though, as he is talking about image movement, and not OTA movement. If I am interpreting the posts above correctly, image movement can be effected - at least if using a wedge - by where in azimuth the OTA is pointing at the time. Also, you will get apparent movement of the image through the eyepiece, or on an image being sent to a screen via a camera, if the orientation of you or the sensor is not oriented level. Terminology is a bit tricky here: by "level", I mean level to the horizon when pointing to the meridian.
Mike, I have never seen behaviour like you or the OP are describing. My settings always move the OTA left when the left slew button is pressed, up when the up button is pressed. That is because I have my settings set for this to happen.
I'll watch to see what others say, and what the outcome is.