"the wiper to ground sweep looks like."
Sorry, I get carried away.
With the amplifier off, set your meter to cover the value of the Treble potentiometer in Ohms. So for a 100K potentiometer, set your meter to 100K Ohms. Or, if your meter is auto-ranging, it will do this automatically.
Then place one lead on a good audio ground for the Treble circuit, and the other lead to the Wiper (center terminal) of the pot.
Then sweep the pot slowly through the entire rotation.
It should show a mostly linear increase or decrease (depending on the rotation direction) in resistance but not a short to ground or an open circuit.
A problem at either extreme end of rotation could cause the resistor R721 to get hot.