Has anybody noticed a correlation between a settlement killing all attackers immediately as you arrive and not getting the quest to complete properly? I've had a couple attacks recently where I haven't even had time to fire a shot because the settlements are so strong that then would not complete for me.

Anybody else seen something like this, or is it coincidence that the bugged quests just happened to occur then?

I've heard of this before, though I can't imagine the defenses that would instantly kill 10+ super mutants (or whatever) who are spread out and such. Course you would also think what with such defenses the odds of even getting an attack are slim to none.

Does this mean that even though you are there, but don't have time to fire a shot, that all the defenses (after killing all the attackers) suddenly fall over broken due to the failed defend settlement status?

I think I'd write it off as a very rare occurrence.

I had this too, though not due to excessive defenses. It's if some attackers wander outside the settlement area and don't get chased down by your settlers. A couple of times it still had the quest notification to defend the settlement, and even after searching the entire area and finding nothing, I left and then the quest failed. NBD really, just annoying.

It most recently happened at the Lighthouse, where attacks always seem to come up the road from behind the derelict truck, IME. I just happened to make my gatehouse there because it was the most logical place. Then when I discovered that attacks always happen there I fortified it even more. There are two sentry posts with guards overlooking the spot, plus SIX heavy laser turrets with overwatch, interlocking fire, and 4 heavy machine guns on the ground in front of the wall to keep attackers busy while the lasers chew them up. Nothing stands a chance. Attackers are usually dead before the rest of the settlers even get into the action.

Maybe I should move my warp-in point back out in front of the wall to try to get a shot off before everything is cooked?

Again I'd love to know if after you got the 'failed' message if all your defenses suddenly broke and all your crops, water, power sources were destroyed. That's what generally happens if you don't show up at all. Just wondering if you show up but 'fail', if that still happens while you're standing there.

I've never waited there long enough to find out, but I would guess it would not happen until you fast travelled away - or walked into the next "cell" (or whatever we call the active chunks in memory).

The only time I've had this happen is when the attack is by Synths.

For instance, I've had the Castle get attacked a few times. (It's defense is almost 3 times the food/water total...which is incredibly annoying...I guess it's programmed to be attacked at least occasionally...) The attacks always come from the road leading into the gate, have been either Super Mutants, Gunners, or Raiders, and I have multiple guard posts there and various turrets all along the wall (including several missile turrets.) Every time, all of the attackers are dead well before they even get close to the buildable area of the Castle. Mission has never failed.

However, in three instances now with Synth attackers (once at Sanctuary, twice at Abernathy,) the mission has failed despite all of the Synths being killed. I've even resisted fighting back myself and shut down the generators powering some of my turrets just to ensure that a few of the Synths make it into the buildable area. In every instance, despite all of the Synths being killed, the mission fails.

I've found the following solution to get around it:

I always get the message "defend X settlement" after I fast travel it seems. When I get this, I reload the autosave from right before I fast traveled, and then go directly to the settlement in need of defense. This prevents the mission from appearing, but the attack still occurs. Kill the Synths. Talk to a Settler to verify (you should get the "thanks for helping" dialogue.)

Annoying, but effective so far.

If you think that's bad, just wait for Synth infiltrators. I could never resolve even one of these instances. Everytime I arrive, there's a dead settler lying on the ground. Has a synth component, so the attack message was about an infiltrator. The turrets probably did away with him well before you arrived. And so the game doesn't register you have been there for the attack. The quest stays logged and cannot be resolved, since the one and only attacker is already dead.

Couple of days later, you get the failed message. Along with a healthy dose of destruction and happiness drop. As far as attacks go, this game is really broken. Someone at Bethesdas obviously thought it's fun for the player to leg it to each and every attack and to punish them if they don't oblige.

I believe they are the cause of it, because I always find one dead after I've killed the Synths. I've never had the Synths attack without finding one dead Settler Synth.

However, I don't get a specific mission for them. It's just another generic "defend X settlement" until I show up and see what it is.

Now that you mention it, both attacks were Synths. Hmmm.