Guild Wars 2

After 7-8 times of testing this, I’m now sure that a “Flawless Defense” bug is prevalent on my account.

Basically:
1) Tequatl is killed
2) All turrets are up
3) Achievement not earned

Multiple Teq kills without any turrets dropping has still not given me the achievement. On my next Teq kill, I can link a screenshot if needed. I’ve stared at the timer just to watch it tick down in case a turret falls when I don’t see, but after multiple attempts, the last Turrets Alive number is 6 at the end of each kill – I’ve yet to see the achievement.

Is there any circumnavigation to this bug?

You are also getting credit for the event itself, yes? Often these achievements need you to be active participants in the main event for it to grant you credit. (For example, the “Butterflies and Viscera” achievement in the Fort Salma Living Story chapter needed you to do enough damage to the boss in addition to protecting all the minions to get credit.)

As such, you may need to ensure that you are actively damaging Tequatl during each burn phase, as well as participating in at least one battery/Megalaser defense event during each defense phase.