Conversion/accuracy errors

Hi, I just tried exporting something to dwg/dxf, but when measuring distances etc they don’t correspond to the original sketchup drawing. A distance of 85mm measures in the dwg around 83-87mm, it even isn’t the same when I try it again. I used several dwg viewer to be sure.
Is this ‘normal’? Is Sketchup not meant to be used for such accurate stuff? I use it to draw stuff that needs to be lasered and/or cut so precision is needed.

Set the Camera Standard View Top, or whichever is appropriate, and to Parallel Projection before you export.

Ok so apparently it did turn out to be the dwg viewer. I used the official Autodesk Free Online viewer and there everything is ok.