Hello,
Is the issue related to mobile connectivity?
Did the issue exist before updating to RUTX_R_00.07.02.7?
Did you update with Keep settings option enabled? If yes, could you reset the router to its factory default configuration?
If that does not help, could you generate a couple of troubleshoot files? One from device right after restart and connectivity loss, the other after a separate firewall restart?
It would allow to look for differences between the settings and what might be causing the issue. To generate the files, access router's WebUI, go to System -> Administration -> Troubleshoot section and download troubleshoot file from there.
Best regards,