The Cable Operators (MSOs) have complete control of what cable modem/gateway hardware they will allow installed and the firmware it uses, this is because they own the coaxial cable that is connected to the ARRIS (G34/36), because of that the Firmware updates are pushed by them, and any update needed as well. Any associated firmware updates are automatically deployed by the cable operator. This is not an ARRIS only implementation, but the required implementation of any cable device manufacturer.

Since the intermittent connection issue is happening on wifi i would suggest you to try changing wifi channels will avoid interference and that will give better speed and connection.

If other Wi-Fi sources such as neighboring wireless access points are using the same wireless channel, this may cause intermittent connectivity issues, even if the competing signal is relatively weak. Changing the wireless channel within the  gateway can improve connectivity.

http://arris.force.com/consumers/articles/General_FAQs/G34-G36-Changing-the-Wi-Fi-Channel

After changing wifi channel as recommended on the link restart the modem then we would request you to monitor the connection for next 24hrs.