Did the TC replace another wireless router?? If so what?
Sometimes it is better to use different wireless names on the two bands.. eg TC24ghz on 2.4ghz (names are all short, no spaces pure alphanumerics.. passwords the same but longer). TC5ghz for 5ghz band.. if you still have issues pick a channel manually as some channels have reduced output to prevent interference with radar.
Go into the wireless options and set by trial and error the best.. eg, 11, 9, 6 on 2.4ghz and 36 or 40 and then 149, or 165 (whatever is available in your area) on 5ghz. Remember the best channel is not automatically chosen .. sometimes it needs human intervention.