Force a 5GHz connection from Repeater to Spectrum router

Our new Spectrum WiFi Router decides whether to connect to a device on the 2.5GHz or 5GHz band based on signal strength and, for the last couple days, it has been choosing the 2.4GHz band for my Repeater, sticking me with a slower speed even though the 5GHz signal is more than adequate.

Fastlane is not an option because I would like to configure the Repeater so that it uses the 5GHz band to connect to the Router, but still has 5GHz and 2.4GHz available for devices to connect to the Repeater (we have a TiVo in the next room with Wireless G that I would also like to connect).

Is this possible?  Or should I just give up on 5GHz WiFi for the upstairs?

Thanks in advance,

Jeff