Your issue may not be firmware related, but the STAC.02.08 firmware is causing trouble in some areas. Best to start troubleshooting by trading modems with somebody who has the newer firmware or approved firmware on some other modem model. If the problem stays in your house even on a different modem, you can be pretty sure it is the line at fault at not the modem or firmware.
If your modem is still under warranty from Teksavvy, they'll get you updated, contact them directly. If your modem is from Teksavvy, but no longer under warranty, they may be willing to help in those cases as well. If you bought from a third party, upgrading firmware will be a problem.
In general, cable modem firmware is not end user upgradable.--