On my old P&P machine, it was possible to not lose any components, but not worth the trouble for cheap passives like 0805 resistors. On my newer machine, I can usually save all but a couple parts. **BUT** there is a procedure for doing this. You have to cut the cover tape at the right spot, carefully pull the component tape back and leave enough empty component tape to re-thread the feeder later. Of course, a contract manufacturer won't spend the time to do this all neatly for you.
Jon