I have a Kenwood VR-507, and i've had it for a few years, either three or four, can't remember. It goes through periods where it won't respond to the remote control, this problem just started recently and it's seemed to get gradually worse. It'll let me turn it on, but after it's been on for a period it won't respond. I'm almost certain it's not the remote, since I've changed batteries and the remote operates all of my other equipment just fine. Any ideas?