Your friend is right.

When ever the amp can't handle the power that is getting sent to it. It goes into 'Protect' and shuts itself of so it won't damage itself.

To make it so it doesn't happen, either:
- Upgrade amp (just for piece of mind having a good amp too).
- Turn gains down so it doesn't have to suck as much power (although it won't go as hard).
- Don't crank it for as long.