@Bosstoad 

Hi, May I know the hardware version and firmware version of your Archer MR600? you could login the web interface and find them on Advanced->System Tools->Firmware Upgrade page.

Regarding the LTE disconnection issue, may I know how often it happens? please help to collect screenshots of Advanced->Status page when internet works fine and when you loses internet, then when problem happens, please don't reboot the router next time, instead, please go to Advanced->System Tools->System Log page to save a system log file and send it to us.

In addition, if the 4G signal in your area is strong and stable, please also try to change the Network mode from 4G preferred to 4G only to see if it helps.