The Americans spent a decade and a lot of money on the first gen system in the 80s (we're on like the forth or fifth gen of GPS sats now) and the sabotage could be as simple as making it a classified state secret that mounting the physics package such that the electrodes are vertical causes microfractures in the physics package due to launch vehicle pogo resulting in 6 month lifetime on orbit, max. Or maybe mounting the physics package horizontally. Or it was spin stabilization that killed it or ...
Or you thought kapton would be a great plastic film for high voltage high temperature insulation for the physics package but (mumble mumble secret squirrel stuff here) as documented in classified air force memo #classified, insert finger wagging here oh no you can't get more than 6 months lifetime on orbit shouldda used teflon (or vice versa)
It could be as simple as a pdf that should have been posted to arxiv.org about some engineering peculiarity of Rb cells getting classified and buried. Maybe because it cost the US government a billion bucks to learn it the hard way back in the 80s.
Edited to add: also, the fact that Stuxnet was discovered would be good reason to think you wouldn't attempt this. You'd need to be bullet proof certain that it would never be discovered.