It happens a lot when people monkey with Glock triggers. Changing only the connector to a 3.5, without changing springs, creates this phenomena frequently
sounds like too many after market parts. the sear is not making contact with the firing pin (catch) so I would look at the connector angle
I strongly suspect that I know what's causing your problem. I'll preface my remarks with the observation that IF you had already fooled around with the striker lug and/or the trigger bar 'kick plate' on that G-35 then you really wouldn't need to post this question online because ... ... you'd already know where you'd gone wrong and 'screwed the pooch', so to speak. So a damaged trigger bar and/or striker lug is, most likely, NOT involved in the current problem you're experiencing.
And now, boys 'n girls, a few words from our resident sock puppet who is NOT an 'advanced' or 'certified' anything other than a really great bullhooey artist. Neither can anyone, here, follow this self-described genius on Twitter because the link he's posted is a dead-blind URL address. (Socky, must think other people are really stupid — huh!) Well ... ... Mr. phony baloney sock puppet, here's some news for ya:Typically a double tap happens when the firing pin lug makes contact with the trigger bar during the cycle/reset but not enough engagement to hold. The firing pin slips off and fires the next round before the trigger is released far enough to allow the firing pin safety to re-engage.
Completely releasing the trigger should stop the malfunction because the safeties will engage and halt the firing process.
If your gun fired while your finger was completely off the trigger then you have an extremely dangerous situation than has got to be addressed. It means your safeties, specifically the trigger and firing pin safeties, are malfunctioning.
Yuppers! You've just reaffirmed my utter contempt for all of the Glock pistol 'techno-crap' that gets posted on the internet–Oftentimes by those who should, but obviously don't care enough to, know better.I’m sorry you just publicly embarrassed yourself but with a quick search for a Glock parts diagram you can learn the correct names to avoid a similar mistake in the future. I personally don’t mind when people don’t know the actual part names but your ignorance shouldn’t be the foundation for challenging my certifications.
While you’re at it, check out the Glock Armorer’s Slide Cover Plate. It’s for inspecting the amount of engagement between the firing pin lug and rear of the crucifix on the trigger bar. If there is less than 2/3rds of the trigger bar covered there is a risk of the firing pin slipping off the trigger bar. The part only exists for the purpose of checking this engagement because if it’s out of speck it can result in double fires.