super slow download on Wifi extender

[Stealthunit]

i have this ex6200 for about 4 years now im not sure if its at his Peak about to fail or something..... it use to use very well and super FAST and lately the download speed is only 300 ~ 500 Kbs MAX wont go any higher...........

i tryed pulling the plug let it restart.....  i did factory reset no luck....... tryed hardwire too super slow too

any idea?? or i just have to buy a new one???

connecting to my modem i get 300 Mb/s