I left my Silver 64GB X for repairs. It was going unresponsive for a couple of times. I am very behind with technology so i decided to leave it to the specialists. Now i bought the device from a very big carrier here in Europe (biggest in my country) that have their own repair services authorized by various phone companies including Apple. What they did was they reinstalled the firmware and they said it was probably software issue. The thing is ever since they returned my device either i am getting paranoid (becuase i am very paranoid by nature), but i feel the phone is bit laggy and the camera looks bit stranger? Now the carrier is very very popular among Europe so i have a lot of trust in them but i fear that someone on the repair services may have tried to replace parts of the device? I know that makes no sence but with my paranoia all outcomes are in my head. So what i want to ask is is it possible for parts from the iphone (motherboard, camera or whatsoever), to be replaced with like cheaper one or defective from other phone. I know they have no reason to do that considering its so big company but i just want to know if its theoretically possible (maybe some of the tech engineeres become corrupt?) I kinda feel my device is acting strangely. I sometimes see a flashing image of the app icons like appearing on the screen and dissapearing for like a half of the second. Another thing is when i gave them the device it was 11.2 now its updated to 11.3 could it be the updated that makes the device to feel bit odd? Again, i trust my carrier, but i have my paranoia about the stuff in the repairs, although highly unlikely, still wanna know is there danger that they've replaced parts of my device with cheaper or defective ones, can parts from iphone at all be replaced?