I have an intermittent issue trying to duplicate clips across take lanes. I hold down ctrl alt and shift and drag the clip to the other lane, which has always worked on X2, and now on X3 occasionally it will move the clip instead of duplicate it. It still shows the little + symbol indicating it should copy it.
 
Is this some kind of known behaviour that I can account for, or is this a bug of some sort?

Check that you are on X3E.

Thanks for the reply, I just upgraded to Ipswich last night. If the issue doesn't appear again I'll mark it solved here.