Delay on Reason parts when doing Audio Mixdown on Cubase

This is weird…
I’ve done a complete arrangement in Cubase Artist 8 with Loop Loft drums on Resons REX (via Rewire)
Now… When I play it it sounds completely normal, but when I do an Audio Mixdown of everything,
and then listen to it, the drum part is suddenly out of sync !!
Why, oh God…or anyone really…Why!?