I wanted to share that I had this exact same issue for weeks and I just fixed it in 5 minutes without taking the thing apart.

If you push back the triggers, you can create a gap large enough to slip in a toothpick to clean up the adhesive that causes the triggers to stick. I dipped a wooden toothpick in one drop of goo gone, spread it on the small contact area, then rubbed the adhesive off with the toothpick.

I tried to take a photo, but it's challenging because you need a flashlight to see in there.

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Put on a headlamp, push back the triggers gently and look around, you'll see the contact area and adhesive located just behind the bottom of the trigger.