From the Live Map, tell Waze you want to go from Red Deer to Stettler. One of the routes takes you along Highway 595. As you approach Delbourne, Waze wants you to turn south, turn right onto a grid road, drive 2 miles, turn left, then left, go 2 miles, then turn right and be back on Highway 595. It's like there's a one mile section of 595 Waze wants to avoid.

Stettler to Red Deer does not show the detour.

Google Maps shows the correct path.

Perhaps there's an incorrect turn restriction along Highway 595. I'm not able to troubleshoot this as I lack the map editing privileges.