Fake Non-Delivery and Returns Scams - A-Z Claims - Options?

I am looking for some help and information regarding some recent claims for ‘non-delivery’ and also, ‘non-Return’.

Issue one: customer claim non-receipt of item however, we have a picture of the box at their doorstep with the front door open and also GPS co-orindates - however, customer opened A-Z and got their money back - courier company will not entertain a claim because they can prove it was delivered.

In situations like this is there anything else we can do? - The customer seemed a bit shady on message exchanges wihtout wanting to sound critical. Has anyone taken action outside of Amazon i.e. Civil Claim or other type of action?

Issue two: customer opened A to Z claim without returning the item - we sent them a prepaid label they haven’t used or returned the item so what is the likely outcome from the A to Z which is pending? I am hoping they force the customer to return the item but if they don’t return it and get a refund, what can we do if anything ?

These are high value items hence our concerns.

Any help and advise always appreciated - thanks?