When should I make a refund request?
When the server as crashed and for some odd reason you can't use /restore.
When a game breaking bug as broken something and you have lost an item.
Some other crazy reason that is possibly out of your hands.
When you have valid proof.

When should I NOT make a refund request?
When some one breaks a rule and you lose something. ( We don't refund for rule breakers )
When you have disconnected and your printers have despawned with money in them.
When you have NO PROOF of having the things you lost and of it happening.