First things first would be to disable power save mode, which has been been discussed in the forum. I also find overclocking the board helps a lot as well and keeping the governor set to performance.
There could also be other reasons why this is happening, such as connecting to a modem where the 2.4/5GHz SSID is the same name. Which can confuse the board and make it connect the widest signal available. 2.4GHz being a wider signal, but in general not as strong as 5GHz and prone to drop outs.
In that case there is a remedy, but I would see if turning off powersave mode helps first.