Illustrator changes x/y coordinates at saving

At first save of a specific illustrator file, illustrator adds 3871.5 points to the x coordinates and 3871.5 points to the y coordinates of all points in the work. I am a newbie with Illustrator. It guess it is something in the file. Is it something with the artboard? It doesn't do it with another illustrator file. It doesn't increment further at next saves. I received the file from somebody else.  I cannot find any similar problem online. I have to position points exactly in the file and it is quite cumbersome if I continuously have to subtract 3871.5 points to check if a point is at the correct position as it was before saving. Where in the file could this reside? How can I stop Illustrator doing the addition? Any help would be greatly appreciated.

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