Wondering if anyone has had or heard of this issue?

Code50, less than a year old.

Me and a buddy are somewhat beginners, and playing Deftones and Chevelle type songs. I have a "Deftones style" distorted heavy tone preset loaded that I'm playing on.

So after an hour or so playing, the tone will start to sound "metallic" and kind've have a "ping" to it, if that makes sense. Sort of sounds like you have a speaker inside of a giant metal cup.

Sorry if this is a newbie question, just sort of confused.

The guitar was new in October, so I assume it's not the strings. I also tried swapping to my Jackson guitar, same annoying metallic pingy sound when strumming. Changed the cables too.

Any ideas?