hi.

1- my isp supports download 78 mbps. when i start to use modem after factory reset, i make speedtest and i get 74 mbps with connection 5 ghz wifi.

after 2 or 3 days, i make speedtest and i get 48 mbps maximum with connection 5 ghz wifi.

i reset modem to factory settings and i get 74 mbps again. after resetting if i load saved settings, without waiting 2-3 days i get 48 mbps again. 

what can be a problem?

2- i cannot get higher than 45 mbps with connection 2.4 ghz wifi. is that maximum speed for 2.4 ghz wifi?

notes:

i always get higher than 70 mbps with cable connection.

i tried all combination wifi settings. it is not useful. PLS don't suggest to change channel or bandwith etc.

after low performance, only solution is reset to factory settings. 

any solution?