I just picked up my first guitar and this amp, so I basically know nothing yet. I enabled tuner mode and tuned low E string (Crunch and Metal LED lit up both perfectly). Then I tuned A string (perfectly too). Then I go back to low E to check it just in case and now Clean LED lit up. Why? I haven't touched it at all. If I tune that again, then A will be shown as wrong. I dont understand.