I stopped repairing phones because of the massive liability and error 53 is a real thing.
After 500 repairs through iCracked I decided to move on to things that were more in my control.
The touch ID has circuitry and I used a hot plate and a think prying tool. Even with the greatest care about 20% of the phones would act a little funky when I was doing my post checklist. I got tired of phones that acted up, I never broke anything but customers would not tell me something or something was on the verge of breaking.
Business was alright but the time I invested made me a loser overall. You are completely at the whim of whatever the phone makers decide to design.
Because phones are still subsidized, mostly, people don't realize that they are $600-1000+ a piece. All that liability to make $30-50 a gig doesn't pan out in the long run.
Android may be nicer for repairs in leniency but the displays are 2-3x.
Apple's lock down isn't going to work in the long run. I can't help but feel that the Apple car will be an utter failure, it should be when they act like this. It's a fucking computer phone, a car is a whole level up.
I miss meeting all the customers.
One thing, if you are in your early 20's and a fit, nice-looking man, fixing iPhones/iPads in a college town is the perfect job to be a sexual predator. 
Women love a man that can fix things.