In troubleshooting this, I changed the model recordset to:
SELECT model.*, basevehicle.*, CONCAT(BaseVehicle.MakeID, BaseVehicle.YearID) AS yearMake
FROM basevehicle INNER JOIN model ON basevehicle.ModelID = model.ModelID ORDER BY ModelName ASC
Then I had to change the code in a couple of places so the Dynamic array was using the yearMake column. The Dynamic array server behavior does not list aliased columns, sop the code needs to be changed manually.