The issue will have to be the sportster unit. It would be too much of a coincidence for bothe the car cradle and Boom-Box to have something wrong with them. I have seen this before...most of the time, the connections on the sportster will have a bad solder joint. This will cause it to turn on and off intermittently. You can confirm this by wiggling the unit when it is docked and getting it to turn on and off. This is not something that would be easy to repair as you will want an electronics repair to fix. The Sportster comes with a 1 year warranty from the manufacturer, so if it is covered, then you can get a new tuner and apply your old subscription to the new one.