As i mentioned shipping the watch back is the last thing i would do. Its just too risky. You could take a look at the modders here on the forum or leave it in a drawyer as a reminder to steer away from complicated reps. Generally rep movements are full of dirt and often lacking proper oil when leaving the factory. Add in more complications than a date function and you have a recipe for failure. They will make sure that the watch is in working order when they ship and that it arrives, thats about it. If you intend to use it and expecting it to work properly i recommend sending it to a modder for a full teardown, cleaning and oiling the movement.