OK, in that case 2 things. Does he have the latest software? Problems with earlier models when computing stuff to do with elevation. Also, as with any electronic device these days that doesn't work as expected, and just as true with any GPS device, try a hard reset. Note that he'll lose any waypoints, routes etc so he might want to back up anything that's important first.
Think
the way you do that is as follows:
With the unit turned off, press and hold the following buttons: PAGE + Enter on the click stick. Then press and release the POWER. The unit will power up asking if you want to release all user data. Select yes, and the unit will be reset.
Never tried it myself though