Running Waze and In-Car navigation simultaneously

[TheEnglishman]

So with iOS17 I could run Waze and the in-car sat nav simultaneously which was nice as I got to use the HUD directions as well as Waze’s functionality 

I couldn’t use Apple Maps and then on-car nav - it was one or the other.  

now, with iOS18 I can occasionally run both but now the majority of the time it’s one or the other. With the last one set winning. If you set Waze last it ends in car nav’s route and vice versa.  Sometimes I can run both but I’ve no idea how/why
 

has anyone found a reliable way to ‘game’ the system so you can use both?