My DC39 has recently developed a problem

that it has tripped the house power instantly and consistently does so as soon as it is switched on. 
After investigation it was thought the motor was probably the cause. The brushes are good, no damage or breaks evident. No signs of any loose terminals or cable damage either. The power switch meters out as operating correctly. 
The DC39 has been owned for a number of years and, along the way, has been maintained correctly with regular filter and brush head cleaning, etc. and has had one motor replacement.

In use it has had its fair share of moments when navigating it round the house that it has toppled on its side due to its design. I was wondering if this may have caused a possible short in the motor winding or something? 
 

I purchased a new motor last week and, after stripping the machine down and cleaning everything inside, installed the new motor. 
Once reassembled, I switched it on and, sadly, encountered the same result - power tripped out instantly. Not the circuit it is plugged into but the main house rcd. 
 

I tested the circuit it was plugged into with another vacuum (Numatic Henry) - no issue. Power not affected. 
 

So, as it’s a new Dyson motor, the power switch and cabling seem good, any ideas what may be causing this instant power failure? 

Any help or advice would be greatly appreciated.