My shapes are doubled in size - why?? Desperate!

Hello,  I make shapes to be laser cut, I export as a dxt for the cad software. My laser cutter told me that my shapes are huge (this suddenly), they can tell because I send them a reference shape that has the exact dimensions. I looked at my files, the shapes display at exactly double the size they should be. I don't know how to fix this, they print out as the correct size. To fix this I copy the objects, paste them into a new file, and guess what, they are the exact size they are supposed to be. Later on, if I have to make changes to the file, they will suddenly be displaying at double the size again. Then I have to cut and paste and make a new file...I really deplore this, it's confusing. What the heck is going wrong here. My laser cutter says that it's not just me, other artists that are exporting from illustrator are sending giant oversized shapes. He thinks the software are not playing nice, but this is happening on my computer, he is only seeing exactly what I send him. They look perfect otherwise. Please help, my cloud is getting littered with similar named files that I can't figure out how to delete, it wont let me.  See attached picture. The image at 50% is the actual cutting size of the shape. Many thanks for any help. Holly