Trim Tabs
Had the same problem a few weeks ago and determined there was corrosion in the unit's "quick disconnect" plug. You could try to unplug and then clean the contacts with electric contact spray cleaner. My 19 year old plug could not be cleaned well, but was able to get tabs to properly respond by playing with the plug in different positions while my son held down the tab switches. So I called Bennett and they sent me a replacement quick disconnect plug for free - now that's customer service! :lol: