Perhaps I missed something in the rules but are Probe Droids affected by stun? And if they are, should they be affected? It seems to me that since a Droid is a machine like a car or computer it should be immune to stun. I would think only sentient beings could be stunned.

When I give my TV a hard slap it flickers. Machines can be stunned

Probe Droids are not immune to Stun. Perhaps a motivator got misaligned, or the weapon system got jammed.

I don't know if I would equate a flickering TV with being stunned but a misaligned motivator or jammed weapon seems a little more reasonable explanation for what happens to the droid.

The other thing to consider here is that FFG deliberately tried to simplify certain aspects of these types of games so they flow better and play faster. Had this game been released 4 years ago, I am sure we would have seen "Ionized" as an effect that works exactly like "Stun", except that it only affects droids. We also would have seen 5 or 6 more conditions that more or less do the same thing as all the others, but are slightly or thematically different. But when viewed through the lens of gameplay and game design wisdom, are wholly unnecessary.