Surely selling a bass involves some common sense in regards to packing it? I've sold numerous basses which have been shipped throughout tge UK, to Europe (Belgium, Denmark, France, Germany, Portugal), and to the USA.
I've never had any problem as I always make sure the instrument is in a hard case, and it's well packaged up. If someone advertised a sale with the caveat "shipping at buyers risk", I'd automatically think "this seller is dodgy" and I'd avoid having anything to do with the seller.