There'll be a reason for it stopping - there's always a reason.
As for the micro switch what could it possibly be for?
Food processors often have a switch-interlock mechanism for safety reasons - to make sure you can only operate it when it's all assembled properly - for safety reasons.
But if these small immersion blenders are disassembled then there's no safety issue to guard against - your fingers are safe.
I think you should challenge the person who told you about the micro-switch - get them to say where it is and what it's for. I would put money on there not being one.
As for taking it apart I suspect that they're not made to be taken apart.
Peccavi, April 2013