Looking closely at Figure 1 in the CME FSN (cited above) ... if there has to be a "re-design", I would suggest that the battery contact leaf spring connectors would be a good place to start. To be specific ... their shape.
Spring-loaded plunger connectors ("buffers") would be altogether better, of course. Or even six AA batteries ... or maybe a "quality" solution using components from companies such as Keystone
With reference to Figure 1, if for some reason the battery moves up (towards you, the viewer) - maybe because it does not fit snugly in its compartment - or is even being pushed up by a crumbled sticky pad (!) - the battery contacts will tend to disengage from the leaf connectors.
By the way - in answer to some of my own questions - I note that the FSN mentions that the real problem is that the pump can unexpectedly power down ... "without any warnings".
Don't forget that the PP-3 was designed to be used with the snap-on (off) connector ... not simply pushed up against leaf spring (or any other) contacts.