switch control judder & malfunctionl

I have 2 mocads one of which is 7or8yrs old and is still going well. like many of us I have had problems,in the end I got fed up with buying switches and decided to take the motor apart "this is not for the faint hearted" firstly one of the bolts which hold it together is fixed so that it will snap and you will have to replace it no problem (go to a good hardware store) you will also have to remove the snapped off stud.
Next look out for the thrust(wavy washer inside when you take the end off,it is tucked up in the end. I found a lot of carbon build up so I blew the carbon dust away and cleaned the armature grooves with a scriber and then reassembled it, again not easy when trying to hold the motor brushes apart and squeezing the top back into position. It worked and I have done this 3 times over the years.
The new mocad 3 I bought last year I have only had 10mnths has cracked close to the handle shaft. This I believe is due to the fact that at some time someone decided to move the hole which allows the wiring to go thro' the tube, 3-1/2" to the right. This I believe has weakened the integrity of tube,the original position on my old trolley was between the 2 welds on the horizontal stiffening bar.
Having said all that I do like my mocad and at the moment I am waiting to see if Pazion Trading "come to the party" .
I live in New Zealand and collected my trolley from my nephews when on holiday in England in Sept 2013. Although the invoice was dated 31st july 2013 which was when I ordered it.
It is a piece of machinery and all machines do go wrong at sometime, but I think this is purely a modification the results of which were unseen.
Lionel Jenkins.
(originally from Somerset)