Object Alignment using Vuforia and Hololens

Hello, we are currently working on a project using vuforia on the hololens, and we want to be able to overlay a model of an object over the object once scanned. The scanning process is working, and the model is placed into the world, but it is inconsistent in its alignment. Sometimes the model is in the same place, but other times it is angled or in a completely different location. We are using Unity and Model Targets. We have been trying to work around this issue for quite a bit now, but nothing appears to make it consistently go in the same place. Your help is very much appreciated!