Generally, yes. But if you have a blaster rifle with a fully modded augmented spin barrel, the Deadly Accuracy talent, and a decent roll you can go through 2 points of Armor and do 1 damage to the hull of something with Armor 2. So it CAN happen, it's just difficult.

RAW states that stun weapons inflict strain damage on "targets". Ion weapons do damage in "system strain" usually to vehicles, but Droids are explicitly called out as being effected by ion weapons.

Because of this I would rule that stun weapons do not effect vehicles under RAW because they inflict "strain" rather than "system strain".

The chance of a handheld weapon on stun doing much of anything to a vehicle simply with planetary scale armor etc in play generally makes it a moot point, doesn't it?

Generally, yes. But if you have a blaster rifle with a fully modded augmented spin barrel, the Deadly Accuracy talent, and a decent roll you can go through 2 points of Armor and do 1 damage to the hull of something with Armor 2. So it CAN happen, it's just difficult.

DavetheLost has it right. System Strain is not the same as Strain and vehicles take System Strain so since the Stun setting on a blaster only does Strain damage it clearly cannot affect vehicles.

I'm not even entering the discussion about whether or not it would affect vehicles, because that's entirely silly. The droid question is kind of silly too, but it makes more sense and warrants more discussion. I'm curious if anyone can show an example of a stun bolt hitting a droid in Star Wars canon, regardless of the results...?

I can't think of anything, but I do know that RPGs are considered canon, and previous Star Wars RPGs have ruled that stun damage doesn't affect droids or does so minimally. It may sound strange that RPGs can affect canon that way, but just as a "for instance", this is how we know that even average Ithorians can use their four throats to issue a sonic bellow.

If someone cares for any continuity, droids could only be stunned with ion weapons in d20.

Descriptions of blasters on page 160 and ionization blaster on page 162, support IMO that this is also true for EotE, but the rules itself are unclear in this matter.

Since droids have Strain and not System Strain, and there's no written rule saying that stun weapons don't affect droids, the default RAW is that they do.

No one is arguing the RAW, we're discussing how it correlates to the universe itself (read: it doesn't).

If you could come up with a way to have it not effect combat then I wouldn't care...

It doesn't affect combat because ion weapons can't damage organics. Are you going to remove free skill ranks or something from organics? Otherwise, I would suggest making stun damage affect droids the same way ion weapons affect organics; in other words, add Disorient 5 (droids only) to the stun setting of a given weapon.

Organics have to breath, sleep and are killed by poison, radiation and disease. They are also susceptible to drugs and addiction. Are you going to remove free skill ranks from droids because they're immune to all of that?

Droids are hurt by stun because the rules say they are. Yes it's different than previous incarnations, but this is also a far far simpler system than previous incarnations.

No one is arguing the RAW, we're discussing how it correlates to the universe itself (read: it doesn't).

Could you point me to where it says all droids self-heal in universe? As you so aptly pointed out earlier, some things are there for game balance reasons. If you think droids are balanced now, where the stun setting on blasters can affect them, how do they stay balanced if you give them the ability to ignorevstun damage?