Intermittent metallic grind from engine!!

From the front of my engine, occasionally I have a scrapping, grinding, hissing noise that sounds just like a bad pulley. However, everytime I take it to the dealer it stops. Today I pulled into the dealership, jumped out to grab a mechanic so he could hear it (and I could get it fixed under the 60,000 warranty) and when we got to the truck again within 5 minutes it had stopped. It is continuous once it starts. I can’t pinpoint what causes it. I can’t pinpoint what it is. The dealer is telling me it’s the high pressure fuel pump but everytime it does it, the sound isn’t coming from the high pressure pump!!! It’s driving me insane. Help.
For some reason I can’t upload the video. I’ll keep trying. Any ideas until then would be great.

 

Maybe injector cleaning cycle?

 

Timing chain