I took my first trip to Portland Airport yesterday and only address option within Waze takes you to the back cargo entrance. There are no other airport signs along the route to tell you its the wrong location or a different way to go. The actual airport entrance is over 10 minutes away from where it takes you. The red line is the actual entrance to the airport.
How did you search for the airport? It sounds odd, but it can make a difference if you search by voice vs typing in the name. Getting the location from another app (calendar, Uber, etc) can also play a role.
As Turbomkt stated. EXACTLY what and how you searched for it is very important in trouble shooting your issue.
I have searched numerous ways for the Portland International Airport and am unable to replicate your results.
There are multiple pins for the Portland Airport, Portland International Airport (PDX), PDX Departures, PDX Arrivals, PDX Rental Car return.