I have a Yamaha rx-379 receiver that I’ve had set up in the surround sound 5.1 program and it has worked well for years. About three weeks ago, I noticed the front speaker wasn’t providing sound. However, after a few minutes the sound started to come through. Since then, it seems it takes longer for sound to come from the front speaker. I’ve made no changes to the system. Is this an indication that the receiver is failing or is this a fixable problem?