IMHO, It's the chip degradation, TP-Link doesn't have a solution to all our cases with "2.4 lost" rather than to replace unit to another (till a warranty is valid). Don't expect to get a firmware...

It seems almost all TP-Link routers have 2.4 chipset degradation. Thanks to this thread I understood that I'm not alone in this sh1t situation and the support of the TP-Link is another bull sh1t....

Got the same issue yesterday with Archer 3150 v2. The 2.4G network sometimes visible, sometimes not, but non of my devices can establish a connection even with open network (disabled security)....