Hello,
Please try the steps described here: RUT240 Mobile connection drops every 2 hours - #12 by Marija and, after completing them, reboot the router.
Please let me know how it goes.
If the issue persists after completing these steps, please fill out the form I have sent to your email address registered on the forum. This will allow me to contact you privately for further troubleshooting, as I may need some sensitive device information, such as a troubleshoot file. When filling out the form, please use ticket ID “15319”.
Best regards,