Oh and the character is a mechanic/doctor (pressure point) so he gets plenty of time to shine. And I built the character for the player (before the beginner's box, where he played 41-vex and loved it, he'doesn't never played an rpg before, I built the character with pressure point and bad motivator and I give him plenty of opportunities to use them effectively, the generally aren't encounter ending I win buttons)

I've seen players want to use it on the sunlight drives of a ship pursuing them, the hyperdrive of a ship that was trying to escape, the spacesuit of a pirate, a demolition charge that was planted on the PCs' ship, a mine that the mechanic stepped on, and several other things. Bad Motivator seems like it has the scope of a narrative Signature Ability, but it is far easier to get.

For a specialization that benefits hugely from a cool talent or two I'd figure it is pretty good.

As for all 4 examples let me ask: was it game breaking? If the answer is yes, the "gm fiat"...

That last one, the one with the mine, seems like an excellent use of the talent by the way.

We have never played this as a permanent fail for the affected device.

A gun, for instance, would fail its attack once but be usable the next round. This is the most common use, to avoid being taken out of a combat or going above Wound Threshold.

Once we used it for a tracking device that the players suspected had been placed on them and they hid from the bounty hunters and successfully evaded them. After that scene they ditched the tracking device to mislead the bounty hunters, but the device still functioned except for that one crucial moment.

I had not considered that it would totally destroy a piece of equipment, though R5-D4 does seem to bite the dust when his motivator goes bad.

At the very least I think Bad Motivator should put whatever target it's used on out of commission for that encounter. Making a blaster misfire for one turn is pretty underwhelming.

That being said, using Bad Motivator on a blaster is a waste of a good talent. There's all sorts of things you can do with it. Your side has night vision gear and the enemy does not? Take out the lights. Need to cover your escape? Pile into an elevator and make the only other one have a mishap. If that's too cheesy, have the pursuers take the stairs instead but force them to make a Resilience check to see how winder they are when the fight gets underway.

The last adventure I ran my players were clearing the escape route for some Rebels inside an Imperial manufacturing plant. An AT-ST was making rounds around the facility. When it was on the opposite side of the plant the group's mechanic was hidden in some undergrowth outside the fence and BM'ed the AT-ST's leg. The knee joint froze up, the walker ground to a halt and the crew was standing around scratching their heads and kicking the tyres (or ankles, as it were) while the group took out the guards at the front gate.

I draw the line for BM at starships; they're too big, they're too far away and they have too many redundancy systems to be taken out by one faulty fuse. Larger vehicles are OK, but only components like the example above; no getting an AT-AT to explode with a mere Mechanics check. NPC droids would be OK, although nemeses would get an opposed check at the very least.