Hi, I am Martyn, welcome to JustAnswer, I am sorry you are having these issues today, I am happy to try and help you get this resolved if I can.
It is under Warranty ?
Best to contact supplier with proof of purchase and dates handy as a first course of action as they are responsible for products provided by them... they may refer you to their preferred contractor to repair or replace
I would NOT recommend you do anything other than routine cleaning until you find out the status of your cover, to avoid losing the warranty
There is no Speed override function on the 4423, unlike some other electronic models
If you believe it to be considerably faster than it ought to be, then I would contact the supplier as a first course
They may have a floor model to try for comparison
The sales of machines in the last 6 months has been unprecedented, it may be that Quality Assurance has suffered... there are reports of same, unfortunately