New Spanish legal requirements effecting shipping with no help or support from Amazon

Since around October it is now a legal requirement in Spain for customers to fill out an import declaration form when purchasing from outside the EU, this cannot be filled by the seller only by the customer. Delivery companies require the buyer’s email address to complete deliveries, they send the forms via email, I explained this to Amazon and their first message told me I should breach their own policy and ask buyers for their email addresses which they would not be able to provide anyway as they would be removed from the Amazon message system. When I phoned up and questioned this the customer service rep did not even know this basic policy, it really makes you wonder about how bad the customer service is. I already had 3 claims where the buyer did not fill in the customs forms and the items were not delivered. I did message the buyers and tell them what needed to be done but I believe that in 2 cases the buyers never bothered to read the reply to their question or could not be bothered to fill the form, the 3rd person took the money from the claim and then committed fraud by filling the forms after the claim was granted, clearly a fraudulent act, I appealed all of these claims but of course I didn’t expect much from Amazon and got even less. This is a typical situation for me on Amazon since Brexit, I wouldn’t even mind so much but it’s the hit on the ODR for third party issues you have no possibility to control. I am not the government or customs authority, I don’t have any influence over these entities just like everyone else. Advise like make arrangements with customs are completely useless as this is impossible. I’m now on the brink of another claim, the buyer is refusing to fill out the legal declaration so I either lose £14 shipping costs and refund or face bad feedback and a claim. After 10 years on Amazon I think it might be time to close this account and look for a forum where the sellers are valued not treated like total trash. @Jessica_Amazon