Three things come to mind after reading and rereading. Assuming all things Bradley are ok then
1. Check to see if ALL plugs are pushed in all the way. Sometimes on the back of the chamber or the generator one or more don't get pushed in all the way - they can be tricky.
2. Are you using an extension cord? If it is too long or too small, you could have a situation that not enough juice is reaching the element.
3. Check your circuit that the unit is plugged in to. If you have a lot of things running off that circuit, again, the element might not be getting enough juice. You can check it with a voltmeter to be sure.
Yes, the Bradley is slow. And that is a good thing - that is what it is designed to do - it performs magic - smoke cooks meat "low-n-slow" with a modicum of tending - almost "set-n-forget". The biggest danger to good barbecue is "hot and fast". That low heat has to have enough time to have it's way with those hunks of meat. It goes at them relentlessly, steadily, unweildingly, until they surrender and holler "I'm finished - I'm done - get us outta here". It is not designed to grill - it's just not. It does act like your oven, but not for over say 250. If you need hotter than that, there are other toy---err----tools that can be used. As an aside, some have circumvented the slow heating and recovery, by modding the Bradley by adding an additional element. But again, this is good for quicker heating and quicker heat recovery - they should not be used to cook brisket at 300 and expect succulent, melt-in-your-mouth, flavor explosion brisket - It ain't gonna happen!
Two things to help with the heat recover. One already mentioned
1. The Bradley has very little mass to hold heat. It is far easier to maintain a steady temperature in a large stickburner - mainly because of the large amount of steel/iron that holds the heat once heated. The Bradley does not have this mass. So adding mass helps - there fore the brick suggestion. Also leaving the full water bowl in will help. Also when putting the water bowl in - use the hottest water you can. That way you are not having to heat the water also.
2. The Bradley achieves its hottest temperature utilizing the heat from the puck burner also. The element it a 500 watt element - and the puck burner is 125 watts. When both are running you have 625 watts of heat. If you cut the puck burner off, then you are reducing the available wattage for heating down by 20%. Keep the puck burner on until the heat recovers to your set temp, then cut it off and see if the temp is maintained.
3. Limit the number of times opening the door - ESPECIALLY early in a cook. Remember the earlier comment about the Bradley not having much mass to store heat. The only heat it has is the element/s and the heated air. When you open the door, much of the heated air is lost and the Bradley has to heat more up. Later in the cook, opening the door is not as much of a problem because the 20 pounds of chicken or whatever meat you have is also warm/hot and is acting as a heated mass.
4. If you can find chickens that have not been injected, you should have a shorter cook time. Its all physics Mr. Watson, its all physics!