Size values change automatically

Hello,

I need help with the following problem.

When I open a Print template and start working in it every size that I manually set in the transform dialog box stays set only while that object is selected, afterwards it changes to a random value near to what I've entered.

For example: I draw a rectangle, I set W=75mm and H=55mm and then, after I deselect it and reselect it, the W is still 75mm, but the H is 55,002mm.

That's an example for the height, but sometimes the width changes too, or event both at the same time.

Is there a setting I have to change or what is happening?

Thank you!