Rutx50 utter useless

iv owned this for around 4 months and have been very happy with it. now its a time blackhole. hours i spend resetting and rebooting. i loose internet within minutes or maybe a few hours if i am lucky. i get download speeds of 1 mbps. reboot and it back up to 80 mbps. rinse and repeat..

i have tried rolling back the firmware to 7.17.5 with a factory reset afterwards but still it keeps dropping 5g and killing my internet connection. i did find for a few hours it worked better with only 2 antenna plugged in ( the 2 furthest away from usb port ). i have turned off wifi and have tried using another router ( asus ax86u ) by connection rj45 cable to WAN port from LAN on rutx50 but still i loose internet.

i currently am using a sim from Smarty ( 3 network ) and i thought this was my problem but after contacting them they confirmed no issues in my area ( paddock wood kent uk ). so i am left with this expensive christmas tree and no internet…

any advise other than reboot and repeat???