faulty lipo???

[ch!3f]

right guys i need some help basicly ive sold a lipo on ebay which was a gens ace 4000mah 30c 2s lipo in good working order.

was fine no issues with it looked after it and always stored at 7.6v with my b6 in between uses.the connectors a 4mm corally type inside the case which has never been tampered as they are glued closed.

the guy who has bought it claims that he has got it this morning connected it to his esc and it has made is motor smoke and sparks from it.hes saying that its blown his £110 motor and wants a refund on it.

i know what i think he has done but i just want it clarifying.but has anyone known if this to happen from been connected correctly?any info would be great on this..

thanks for reading