@Amer-Hash 

Hi, thanks for posting question here.

First, it is suggested to update firmware to the latest according to the official website. (referring to this guide.)

If the problem remains, we need your cooperation to follow the steps below:

--Is the ISP of your SIM card from MBB?

--When the internet get unstable on the router, does the LEDs show normally on it?

Multiple factors might cause the disconnect automatically. For the LTE disconnecting issue, please try the following steps for troubleshooting:

    1. You may try to change the Network Type on Advanced > Network > Internet page for a try.

    2. Please insert the same SIM into another LTE device or even a smartphone to check if the SIM has a problem.

If the LTE connection is fine, only the wireless client devices are unstable while connecting to the router:

    1. Make sure the Router is properly placed, it should be put in an open area instead of inside a cabinet or shelf.

    2. log in to the web management interface of the Router, go to Advanced > Wireless > Wireless Settings, and change the wireless channel to another one.

    3. For 2.4GHz wireless client devices, adjust 2.4GHz channel width into 20MHz, for 5G wireless client devices, adjust 5GHz channel width into 80MHz or 40MHz to avoid interference.