I just got a Les Paul Classic Lite (thinner body), built Oct '19. It has zebra pickups, no covers. With the volume on amp fairly loud and volume knob on guitar on 10, on treble pickup, when I mute the strings, I am getting dreadful feedback, sounds like a loud low-pitch hum, similarly to what you might hear with bad feedback you get with a PA. I have tried another guitar, much older, DiMarzio pickups, and set at exactly same volume, standing in same spot, and muting the strings, dead silence. I have tried the neck pickup and the hum is not as bad. Has anyone experienced this with new zebra humbuckers on a new Gibson, particularly on bridge pickup? "Fairly loud" is for me a Marshall 50W volume on about 2.5. Hum only happens when strings are muted. The hum kicks in in less than half a second after muting the strings. I have tried standing as far as about 7 feet from cabinet, facing away from it. I do not think it is a issue with the pickup being too close to the speaker. Please help!