As a seller i have a return request and for the first time it is allowing me to decline

[pal_version]

i sold a pair of wireless headphones and it is way past the 30 day return window. they were new and sealed when sold and the buyer is now declaring that they have started lagging during audio playback. 

at the point of sale i was concerned about the buyer as there were quite a few questions after the sale and something about the delivery address had alarm bells ringing that they were possibly a drop shipper. (maybe i should have trusted my gut at that point, i had put the nerves down to the buyer being a new eBay user so continued with the shipment).

anyway, for the first time ever i have the option to just outright decline the return. I am tempted to decline but i'm worried this could act as a defect on my account and turn into a long drawn out issue. what are other peoples experiences of declining a return?

if we were talking a small amount i would just accept the return and move on with my life but the order was worth over £60.