WiFi slow on MR1100

I have the mr1100 i'm guessing the second iteration with band 14 support, I have the 6420B model. Firmware is 12.02.06.01 and is current fota fw. I'm unclear of its support on the 14 band but the problems not signal its just the wifi, I guess I'll just have to wonder to the area where I get 4CA on my s9+ to find out. I know i get manic speeds there but havent tried in a while with the m1 modem since the last time I tried it, it was still 30/30mbps last time I tried wondering about the hot zones with 2CA &3CA towers. The speeds on this new cat 16 modem with the s9+ are quite consistent. But I fear now I might have a faulty radio or just too much 5Ghz interference, I've accounted for the crowded 2.4g by disabling it but even then only a 10mbps (40/30) max before it settles down to 30/30 or sometimes 20/30 which doesnt make sense considering that uploads usually 5-15x lower than downlink.... in the common area I use it over ethernet I get on average 80-105mbps, but cannot exceed more than 40mbps for like 2seconds also on many devices, GS9+, GS8, note 4, and a simple little 2.4g tablet.