[G4 Q&A, Help & Troubleshooting] br0adband:
Just for the record: if your G4 does suffer from the bootloop at some point, there are no "local shops" that can fix the problem, it's something that only LG itself can resolve. The best you can hope for is registering the G4 with LG under your own name, picking a date of purchase like September 15 2016 or something (note that if that were the purchase date it would have factory warranty until September 15 2017), and if it does end up dying at some point before the warranty would expire (based on the date you entered as the date of purchase) then you might be able to get LG to replace the motherboard (at their expense including the shipping both ways) by contacting them through their online chat support service if and when it becomes necessary.

There has never been a conclusive answer as to why the G4 (and the other LG devices) suffers this problem but it's believed - note I'm saying it's believed and that's based on some sound principles of how and why phones can and do die - to be heat-related and also related to a manufacturing defect aka they used pretty crappy solder in the manufacturing process on the assembly lines.

The belief is that when the G4 and the other devices run very warm like when using 4K video recording or playing a game for an extended period of time or perhaps running device benchmarks in a loop for stress testing that the SoC (the Snapdragon 808) heats up enough to where the solder points holding it to the actual motherboard become softer and develop micro-fissures which are literally small breaks in the connections and after multiple such heat-up cool-down heat-back-up-again cycles that the small micro-fissures become larger and eventually they become large enough to prevent the proper flow of electricity aka electrons.

Think of pavement on roads. In the summertime that pavement heats up and it expands (literally) and then as night comes on it cools down and contracts, then the next day it heats up again and expands, then cools, over and over again - over a period of time that heating up expansion and cooling down cycling causes cracks in the pavement, and as vehicles drive over those cracks it'll cause chunks of the pavement to break off, more and more all the time which is how the classic pothole develops.

Same principle with the G4 and the other devices suffering from these bootloop issues (again that's the belief). Why LG let it happen for so long across multiple devices (some G3, a whole lotta G4, some G5, some V10, and even a V20 or two have been reported, and of course the Nexus 5x too) is beyond me but it's not relevant anymore. There's a class action lawsuit against LG (I'm part of it having owned several G4's that did bootloop and I currently have yet another G4 that's working fine so far) so maybe it'll get resolved at some point. LG has repaired all the G4's I've had issues with and I fully expect them to do it again with this F505S I currently have if it dies.

Anyway, that's some background on the issue. If the G4 you have dies, nobody is going to be able to repair it except LG so, go to LG's website (in your country) and then register it in your name (you'll need to create an account if you haven't got one already) and the use the info/IMEI to get it properly registered, say you bought it in a carrier store (unless it's an H815 then just you got it from LG direct), pick a date sometime in the latter part of 2016 as noted and see what happens.

Good luck...