When you get robots replacing guys with guns, then you've got a whole second set of problems to deal with them. Namely, cybersecurity goes from being annoying to being potentially lethal.
Which, if you think about it, is a slight recasting of the same failure mode: formal control of the instruments of force can become detached from actual control.
It's the same failure mode, but it's a much worse problem. For the (human) police to join the insurrection, they have to be persuaded that the insurrection is either morally right or too big to fight (which may mean that it's too big for the police to consider arresting/killing them all to be an acceptable solution). For the robots with guns to join the revolution just takes one really good hacker.