Dear vibhuti-export,
Greetings from team eBay!
We are sorry to know about the issue faced by you. However in such cases the best way is to communicate with your buyer and explain the details of the return process basis the return policy stated by you.
If the buyer has already opened a case and requested for the refund, it would be best that you follow the guidelines provided by eBay. Return open under remorse reason, where your return policy says " buyer pays for return postage, yes the buyer will be responsible to ship and complete the returns from their end, however, accepting returns is of prime importance in this scenario as well.
eBay will not be able to comment on the customs, this is what you need to connect with your buyer and solve. Therefore it is best that you communicate with your buyer on the next steps.
Regards,
eBay INCBT Team