Before looking at the modem updater, I would like to see if there are any other potential causes for these issues.
Was the connectivity stable before?
If the issue appeared after a firmware update, please try restoring the device to factory defaults to see if the connection stabilizes.
Also, make sure to check the signal strength and quality in Status -> Network -> Mobile. Compare these values with the recommended values found here. If the signal is weak, consider repositioning the router and ensuring all external antennas are properly attached.
Should the issue continue, please provide a troubleshoot file. Make sure the router has been in use for some time, and generate the troubleshoot file after you encounter the issue again. This will help the logs offer more insight into the problem. You can download a troubleshoot file from System -> Administration -> Troubleshoot. Please attach this file by editing your question.