We recommend connecting the S34 directly to a computer via an Ethernet cable and running a speed test. If the hardwired connection provides the speed you opted for, then the issue likely lies with the router, and you may need to contact them for further assistance.
We recommend checking the cable signal levels within the modem. If the signal levels are out of the acceptable range, they can lead to the kind of connectivity issues you're experiencing.
Cable signal levels are like the volume and clarity of a conversation between your modem and your internet provider. If the signal is too weak or too strong, it can cause communication issues—just like it would be hard to hear someone whispering from far away or shouting too loudly in your ear.
When the signal levels are within the recommended range, your modem can maintain a stable, high-quality connection to the internet
Please refer to the link below for instructions on how to check your cable signal levels:
http://arris.force.com/consumers/articles/knowledge/S33-Cable-Signal-Levels
If you find that the signal levels are not within the recommended range, we suggest contacting your Internet Service Provider (ISP) to have them reviewed and adjusted as needed.