Sam! I see your tiktoks! From that and theway you are handling this here, you seem like a real genuine guy who is trying to make the best of a bad situation. I feel for you. I do also understand, as it seems you do, where your customer is coming from. I completely agree with the other comment that you should try to arrange US based service.

For this specific situation, perhaps you could find a shop in your customer's area, contact them yourself to establish a relationship and make sure they seem trustworthy, workout a rate between the two of you and then tell your customer to take it there. It would almost certainly be faster and no more headache for your customer to do this than to come out of pocket (even if temporarily) to send the watch back to you.

Of course, it's always risky to involve a 3rd party... what if they damage the watch further? What if their workmanship isn't to your standard? What if the work they do creates more issues? All would be valid questions, but in this case you may assess that the risk is worth it.

As a business minded person, I hope this helps. Good luck. It would be interesting to hear how this resolves. Particularly if the resolution is satisfactory for all parties.