J. P. Gilliver (John) wrote:

Occasionally, I find I can only move the pointer horizontally or
vertically (not diagonally). I'm pretty sure this is triggered by some
action on my part. I can usually return it to normal by scribbling with
Ctrl pressed.

Tried rebooting into Windows' safe mode and retest touchpad operation to
eliminate any interferrence possible from startup programs? I've seen
where a background program interferred with mouse positioning.

In the touchpad setup, there are probably hot zones defined, like along
the rightside for vertical scrolling and along the bottom for horizontal
scrolling. Been too long since I last used my laptop but recall it had
other hotspots, and special meanings for multiple taps (e.g., 3 taps for
dragging) or 2-finger modes. Try disabling those special use zones and
special tap modes so the touchpad ONLY does positioning of the mouse
cursor. If the problem goes away, could be you are accidentally
multi-tapping or using a hotspot.

How many mice or pointing devices are defined in Device Manager
(devmgmt.msc)? Did you leave plugged in a USB transceiver for a mouse
or keyboard?