Welcome to the forum. I don't save as .dwg very often, but I suspect it has something to do with the settings in the Options button at the bottom of the "Save As" dialog box after you choose .dwg as the file type. It's hard to say without more detail. You said you're having trouble saving. Can you be more specific and explain more about what kind of trouble you're having?
Before you save to dwg files, press the option button, then select which scale you need set to 1:1, For exp if your sheet scale is 1:1,and you choose sheet scale 1:1 from base scale, all the scale will remain the same .if you select drawing view scale 1:10 to 1:1, relatively your sheet scale will change to 10:1.