Buyer returned empty envelope

I have received an empty envelope back via myhermes - Envelope has clearly been sliced open and the goods removed. Amazon provided the returns label and I have tried to deduct 100% from the refund but the system keeps returning system error.

Should I just take the loss and refund? I’ve not supplied the label and can’t claim for the loss or get any info either.

Another problem:

Customer is returning four item all weighing 72g, total weight on parcel 288g. Hes saying the description on site is wrong and that the item is longer than described. This means I can’t charge him for the label.

He has lied as the item is a set size item and the weight confirms he’[s been sent the correct item. I have messaged him and he’s ignored me. Clearly he is wise on how to get a free label.

Any advice appreciated?

Thank you