17.2 update old projects to flexbus?

When opening older projects created in Resolve 16, audio busing mode tab in Fairlight settings has 'Use fixed bus mapping' ticked and greyed out.
Does anyone know of a way to update them to flexbus?
Flexbus is so much better on 17.2 created projects. ADC now seems to be working well along with seamless mix drop-ins
Does anyone know of a way to update them to flexbus?
Flexbus is so much better on 17.2 created projects. ADC now seems to be working well along with seamless mix drop-ins