Latutude 5420 locking while using it within 1 minute (using multiple screens)

This appears to be the express sign-in doing this.  discribtion says its a proximity sensor, but it appears to be a stare sensor.

Our users tend to have laptop + 2 extra monitors, when you use the other monitors it seems to lock, since you tend to use the larger screens 95% of the time this is a major problem, turning what on paper seems a great feature into garbage.

Is there a solution to this or do we have to disable the lock on walk wake away feature.