Different measure units

I am creating a 3D model from multiple images using the photogrammetry session. Now, when the session generates an OBJ file and I measure the distance between two points, the distance is displayed sporadically in different units. Sometimes it's meters, then centimeters, or another unit altogether. How can I tell the photogrammetry session to always create the model in millimeters?

Different measure units
 
 
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