Perhaps this is the Easy Bolus feature of a Medtronic pump gone awry?
It's hard to imagine it delivering a 20-unit bolus, but I did have an incident where I was leaning against a railing (waiting to enter an event) and bumped the pump enough that it Easy Bolus was ready to deliver an unexpected 5-unit bolus! Luckily, I heard the Easy Bolus beeps before I bumped the 'ACT' button against the railing and started the bolus. Since then, I've disabled Easy Bolus because I never (intentionally) use it.
Locking the keypad is another way to help prevent accidental boluses while sleeping/groggy.