USB wifi WNDA3100v3 doens't recognizes 5ghz

Hi, I have two USB wifi WNDA3100v3 mounted on two different PCs and on both of them it has been giving me the following problem for some time (not before): they don't connect with 5ghz but only with 2.4ghz. If I go into the  router program and manually change the channel they connect with the 5ghz, but after a while (hours or days) they disconnect again and I have to manually  change the channel. Clearly it happens even if I set AUTO on the channel choice. The problem is, I repeat, that they are two identical pens on two different PCs (Windows10) which for a long time worked well without giving me the problem. The other devices I have at home: a laptop, cell phones and tablets always take 5ghz without problems.