I sold a few watches, mostly internationally. (also via Chrono24)
I have to say I never had any issues. What helps is if you choose a decent shipper with track and trace codes that work from door2door.
(local postal services tend not to have this)
Also make sure your communication is on point (and confirm the same is coming from the buyer)
Just like you 'buy the seller' I would say you also 'buy the buyer' in this case.
Having good communication prevents issues later in the process.