Editor's Note: This story was updated at on Feb. 3 with comment from LG:
"We have been made aware that the LG UltraFine 27-inch 5K display (model 27MD5K) may experience performance issues caused by signal interference when a Wi-Fi access point is positioned behind the display within a distance 2 feet (0.6 meter). Changing the location or positioning of either the router or the display should resolve the issue.
"Customers continuing to experience issues with their UltraFine displays are advised to contact their nearest LG customer center for prompt service. LG apologizes for this inconvenience and is committed to delivering the best quality products possible so all LG UltraFine 27-inch 5K displays manufactured after February 2017 will be fitted with enhanced shielding."
Original Story 1/31:
Apple doesn't offer its own high-end, high-resolution desktop monitor anymore. Instead, it recommends the LG UltraFine 5K Display, and even sells it through the Apple Store for around $1,000. It's an expensive 27-inch monitor which doesn't include the aesthetics an official Apple product enjoys, but then you're still getting a 5,120-by-2,880-resolution display on your desk.
However, the UltraFine 5K seems to have a rather serious flaw. Placing your router within 6.5 feet (2 meters) of the display causes the UltraFine to start flickering. And the closer the router is, the more chance it "goes black" and becomes unusable.
According to 9to5Mac, the flaw was brought to LG's attention recently by Patrick G from Bolton who has been an electrical engineer for 35 years. He complained via email of a "WAP Proximity Issue" that happens when either a router or wireless access point is placed within 48 inches (4 feet) of the UltraFine 5K.
LG Support confirms this is an issue, but only with the UltraFine 5K monitor. The UltraFine 4K, and any other computer monitor for that matter, does not suffer from this problem. As to the cause, LG still needs to explain why it happens. The fix is to keep the UltraFine 5K away from routers and access points by at least 6.5 feet.
Anyone who owns the UltraFine 5K can check the manual, but will only find reference to not using the display where "Electromagnetic Interference occurs." There's no specific reference to routers and access points, but it's clearly an issue you need to consider. Alternatively, opt for the LG UltraFine 4K and avoid the problem completely.