Connectivity with DPC3941T Router/Modem

So basically, the problem im having is that the router will randomly lose internet, but still send WiFi. The online gateway thing says it has internet, and Xfinity troubleshooter is, as usual, completely useless. It can't find any problems with the connection, and restarting it will work 1 out of 5 times. The Modem/Router already costs a ton to rent, so would getting a new one fix the connectivity problem and save money in the long run? Also, this has happened multiple times before, and technicians have been no help.