We don't have that particular unit here in NA, however, I did check through all the h1.75 models for any grams about the p-brakes.
NADA

If the cable breaks when the operator pulls the handle then I'd have to say some kind of assy. or adjustment problem.

If the cable is breaking while the operator is using the service brakes, then you're looking at a problem that let's the shoes move too far.
The drum brakes wedge themselves in when appplied. If the drum dia. is too large and/or the shoes are too worn/out of adj. then the lever in the drum could travel far enough to pop the end off the cable.

Are you seeing any bent linkages, either at the wheel or in the handle?

I have to ask... are these OEM cables or jobber?
It's just that this is a pretty rare occurance (IMO). I've seen levers and linkages destroyed/twisted without hurting the cables.

I should have said that the machine is a Hyster H1.75BX