I have a UBC30XLT Airband scanner. I bought it new. Have been using it for the last 5 months. Excellent performance on airband with a Diamond RH 795 telescopic antenna. For a week now the audio has lost fidelity, it sounds muffled and bassy, as if the pilots are speaking with their noses closed. I tried resetting it many times, changing the antenna, batteries, everything... it doesen't help. Can the weather or intereference affect sound quality? Everything else is ok, it works fine. I tried another pair of headphones, it still sounds muffled. FM radio stations sound just fine, no difference, this happens only on airband. Is there a way to control audio quality? Some tuning on the circuit board or smth? Does this indicate a failure on the board? Thank you.