Either there is intentional supply chain constriction going on or Nintendo is the worst major corporation on the planet at determining what demand is for their products. This has been happening for twenty years.
Executives of manufacturing companies found that it's easy bank for them personally to cut their company's production overhead, most notably by keeping a very low inventory. An executive at Nintendo can bring in a guy that does the lean manufacturing thing, then they work together to cut inventory, cut assembly staff, overwork who's left and limit purchasing. That makes them look good and get bigger bonuses. The purchasing and production team then has pick up the pieces, cobbling together product with whatever they can get at the time from one of their contract manufacturers, as evidenced by the 3DS screen situation (both IPS, both TN, or a combination).
Say Nintendo wants to meet an order of 50,000 NES Classics just to meet a portion of last month's unfilled orders. Every CM involved in that product has to get them the components (main boards, shells, etc.) right away since Nintendo has none. Any one of those CMs might not be able to ship to Nintendo in time, or not enough of them. Maybe the CM who makes the main board has their resources tied up on the orders of other companies and are weeks out from starting on Nintendo's order, or maybe they themselves don't have the inventory to make NES Classic main boards and have to wait weeks to restock parts. They go month to month scrambling to get what they need to make their numbers. So Nintendo most likely has multiple different CMs making the same component just in case this happens, so quality will vary. For example, one 3DS display manufacturer might be unable to ship enough to Nintendo this month, so Nintendo has to call a different contract manufacturer and use their shittier ones for that order.
Basically, executives at Nintendo are making more money personally at the expense of their manufacturing capabilities and their customers. They'll intentionally underestimate the sales of a product knowing they can't come close to making enough to meet demand since they gutted their manufacturing capabilities, so they go month to month calling their CMs and try to get them to deliver the what they can asap to meet orders, and in many cases the retailer won't see their order on time.
