If you are getting this problem when importing your SketchUp file using the ‘import vectors’ function then my guess is you haven’t specified an option in the ‘orientate part’ field of the VCarve import dialogue. Upon import, VCarve will do a scan and determine the face of the part with largest area and place it ‘face up’. However, most parts will have two faces with identical area and thus, VCarve will randomly select one of the faces to be ‘face up’ on the z axis. Hence, you probably are importing both left and right parts but one is face down and so it looks as though they are the same part.
I have found a reliable way to ensure all parts are orientated correctly when brought into VCarve is to start in Sketchup. In your model, apply a specifically selected colour to only the ‘face up’ surface of each part/component. In the materials browser, rename the colour to something like ‘face up’. This ‘colour’ can be edited to be plain white if you so choose- the critical thing is it’s name. Here’s why…. Upon importing into VCarve, choose ‘material’ under the ‘orientate part by’ option. The colour you named ‘face up’ should be an option. Select it. All parts should import so that the painted face is up with respect to the z axis.
It would be good if VCarve respected the individual sketchup component axes in relation to orientating parts upon import but it does not. If it did, there would be no need to paint faces etc.
If you would like to read more about the idiosyncrasies of Vectric software and how it deals with Sketchup models, read my response in the following post:
Hope this helps