Every shop has them — patterns of practice that produce comebacks faster than any other. They are obvious in hindsight and invisible in the moment. Here are the eight we see most often, with what to do instead.
Mistake 1 — Skipping the water seal
"The phone was already opened, it does not need a seal." It does. The seal protects against the next splash and protects warranty arguments three months later. Two-minute install, $0.40 in adhesive. Skip it and you will see the phone again.
Mistake 2 — Mixing screw sizes on reassembly
Bracket screws on iPhone boards are different lengths within a few mm of each other. A wrong-length screw on the wrong post cracks the board pad underneath. Lay screws out on a labelled mat on the way in.
Mistake 3 — Replacing the battery without checking Battery Health
If Battery Health is at 89%, you are replacing a healthy cell to please a customer who is buying a software fix they do not need. Always check battery condition with the customer's phone before quoting.
Mistake 4 — Skipping the post-repair tests
Five minutes of tests catches 80% of "I just put it back together" errors. Charge, sync, mic, speaker, camera — the standard list. Skip it and you ship a phone that fails step one as soon as the customer unplugs.
Mistake 5 — Prying under the battery without isopropyl
Pulling the adhesive "dry" bends the cell. Bend the cell and you get a one-time deep crease — invisible now, swelling later. Isopropyl under the cell turns the pull into a low-force glide.
Mistake 6 — Skipping the ear speaker + proximity flex combination
On iPhones from the X onwards the ear speaker is part of the front sensor flex. Replacing just the speaker wastes parts; replacing the whole flex once is the right move. Watch the symptoms — when in doubt, replace the assembly.
Mistake 7 — Buying the cheapest screen on offer
The cheapest copy screen saves you $4 per unit and returns you $40 in callbacks plus reputational damage. Stick to Grade A minimum — see the grading guide.
Mistake 8 — Not documenting the repair state on the ticket
"Customer reported" is not documentation. A photo of the screen before opening, a photo of the battery percentage before swap, a photo of the flex cables after seating — three pictures is the difference between a defended warranty and a chargeback.
How to compress this list
Print this checklist, put it on the bench. Charge battery prices at quality-tier (the cheapest come back fastest), test every job, and keep two of every fastener tray per model so the right screw stays where it belongs. Browse the catalogue for matched-tier parts that survive this checklist without complaint.
FAQ
What is the most expensive of these? Wrong-length screws. They crack board pads in ways that look like phone damage, not repair damage — and the customer is right to blame the shop.
How fast do these mistakes show up? Wrong screws: instantly. Bad seal: within a month. Cheap screen: within a quarter. Build the discipline early.