It could be a bad switch in the handle, or it might be something else entirely. There could be an issue with the power head motor, cord, extension wand, or the internal hose wiring. To find the short tug and pull on all connections while keeping everything else still.
The bottom should slide into the catches quite easily. Take some time to brush out the stops and tabs to knock off built-in dirt. When emptying the unit first put a trash bag up and over it. Then have someone else twist the bottom off into the bag and then grab the cloth filter and give it a good shake. This will keep the dust in its place in the bag.
This problem could be a number of issues. It could be the switch assembly, wiring within the hose, the powerhead, a faulty connection with the extension wands, or an issue with your high voltage wiring. If you have inlet valves wired with high voltage receptacles and your Beam 1393 power head has a two prong cord, you could plug it in directly to the wall to elminate the power head as the issue. The only way to test if it's the wiring within the hose, is to have a special tool to measure continuity. If there isn't any intermittent power through the hose to the powerhead, it's usually not an issue with the extension wands. More often than not, the issue is with your switch assembly and is a simple fix. We have replacement switch assemblies, Switch Assembly for Gas Pump and Pistol Grip Style Hoses (Part #352GS and #352S) for hoses marked on the wall end cuff with the letter P within a small circle.