my local TV computer guy noted MOST manufacturers buy the internals from the same place, BUT of course assembly is KEY!! NOT a computer geek but replaced 2 hard drives EZE on an older bigger 17" Dell, not so much on a smaller 15" but got it done. the smaller thinner the computer the harder or impossible to repair or upgrade
There are the big 4 ODM (original design manufacturer), aka contract manufacturers, in electronics. Most large American / European companies build their stuff by contracting them. All 4 of them are Taiwan head quartered, but with a majority of them made in China.
Compal
Quanta
Foxconn
Pegatron
I might have them mixed up or something like that, but these are the big 4 ODM.
Foxconn is not only a contract manufacturer but they are also make a lot of little parts, PCBs, ribbons, stickers, plastics, etc. They can live with a 6% profit margin on top of labor cost and still be profitable, because you most likely buy their little parts when you use their services. Even if you use Pegatron you end up with Foxconn parts and Pegatron cannot sustain a 6% profit margin on top of labor cost.
There are other manufacturers specialized in more focused area. For example Kingston and LiteOn also contract manufacture OEM memories and SSDs for other OEMs and their retail brands. MSI / Tyan / Gigabyte etc also do contract manufacturing of motherboard for OEMs. Cooler Master do contract manufacturing of OEM CPU coolers, etc.
Assembly wise they are really similar. Brand design the products or license them from another company to tell ODM what to build, they will eat small amount of yield loss (98.5%) as their fault but beyond that they will stop production until the brand or where they bought their design / parts from sort out the issues. That way they have the incentive to get things working optimally but the production won't get hit for a bad design.
The biggest concern they typically have is the inventory, who they buy from and how much active inventory they need to keep on hand (and lose money on when price drop). When there's a bad batch of parts if you ask ODM to buy and hold them who get the blame? When you ask them to hold 3 months inventories on the rare exotic 16 layer chips that nobody else in the industry use and then suddenly you cancel the order who eats the cost, etc.
Usually reliability is a design problem, manufacturing is pretty consistent with mature yield unless you push the design too far and you are the first design to actually try it. You cannot blame Foxconn or China if things break, they have been building things that are super reliable if design right, but if your design fail early and only you fail early, the odd is the design has problem. It will be the same result even if you make the in the US right in the same lab with the engineers in the Silicon Valley.