When using Paypal's Multi-Order shipping function, I have noticed a glitch recently. On occasion the computer will say the transaction can't be completed and try again later. I was successful later, but I found I had been double billed!

The uncompleted transaction wouldn't print a label, but it took money out of my account. I had to process a refund for the labels that didn't complete, which means I have to wait several weeks for the refund to reach my account.

If you get the error code saying the transaction couldn't be completed, check later to see if you were already charged for those labels. If so, you can use the "reprint label" command instead.