you can also try and upgrade the firmware that you are using in it and then see that whether it is necessary for you to repair the firmware that you are using in the system. And also it is that just try making the changes in the setting of the modem and then see that whether the connection is being done in it properly or not. You can also run the below given code for the upgrading of the firmware that you are using in it:
See that whether it is working out for you or not.
tftp -i 192.168.1.1 PUT T28-0q-003.img