Usually the problems are at the cord/switch connection. That said, the Windsors will auto shut off after about 20 seconds if the bag is full, there is a clog, or the brush is worn out. Normally if the vac shuts down the reason will be displayed by the lights on the head. If your bag full/clog light or brush light is burned out, you'll have no way to know that's what it is. When you turn the vac on, all the light should flash, if they don't or 1 doesn't then you have a burned out light.
Out of about 50 Windsors, I've only had one sensor failure. The vac started thinking that the bag was full if even if it was empty.
You should trust the bag full light on your vac. Sometimes the fine soil will clog the bag but it will still appear empty. The Windsor sensor xp's will fill a bag 25% further that the sensor s or sr. They have the same specs but there is a power difference. Windsor obviously is aware of of this, hence the xp badge. Why the specs are the same on paper, I don't know.