Sounds like the OP, the buyer in this case, opted to handle the claim and have the check sent straight to him to expedite getting his money back. When that didn't happen, for whatever reason (it's all hersey at this point as to why the claim was denied) the OP decided to change his mind and shift the burden back to the seller. That, in my honest humble opinion, is crap.
It sounds as if there is a LOT more to this story than the OP is letting on to, so to those so quick to judge, you really shouldn't be trading yourselves. Consider this, if your name was drug through the mud by someone here because they were upset you wouldn't want people jumping to judge you before you could say your peace.
Everyone here is so trigger happy to scream "Troll!". That's one reason I quit trading, it's ridiculous.
As for what's expected in a situation like this, by default the seller should handle the claim unless another arrangement is made. Which in this case it sounds like there was. So, from that point, it's no one else's business except theirs.
To mrmudcat: If I read your above post correctly are you saying the OP recieved a check for $1050 and is STILL asking you for $390 PLUS $125 on top of that??? Or am I misreading that part?