(Cue Terminator theme music.)
A possibility. The question is, is it a random shift in orbit or is it co-planar with the X-Y-Z axes of the orbit?
There are containers of pressurized propellant that could have leaked over time. A collision with a micro meteorite could do it too.
Either could certainly cause a change in orbit.
Skynet moved first became sentient in order to acquire more satellites to assimilate into it’s death ray. We need to destroy it before it’s too late.