Why would substrateUnits be undefined?

When calling the jobs-service API occassionally the substrateUnits value returned is undefined instead of "SHEETS" or "MILLIMETERS".

Why?


Thanks


What kind of press is this coming off of?  It's possible that not all models were defined properly in the API.  I'd be most concerned about the 7250 presses or possibly some of the industry specific models like the 20K/30K.