HP ProDesk 480 G4 MT Maintenance And Service Manual page 82

Mouse will only move vertically, horizontally, or movement is jerky.
Cause
Mouse roller ball or the rotating encoder shafts that make contact
with the ball are dirty.
74 Chapter 6 Troubleshooting without diagnostics
Solution
Remove roller ball cover from the bottom of the mouse and clean
the internal components with a mouse cleaning kit available from
most computer stores.