a problem of multiple printing in double-sided

I tried to make multiple copies with double-sided printing by choosing "print by copy" option. 

Then what happened is that the final page of the first copy and the first page of the second copy were printed in ONE paper!! (one in front side and the other in back side) The manuscript ends with odd page number...This caused me a serious trouble wasting time and papers. 

I wonder why this happended (I use Mac with a Canon laser printer) and never want this to happen again.