What if my file upload or delivery upload fails? and can I partially cancel / refund an order?
You can add files in dropbox and share a link in your delivery if and only if your order delivery size is greater than limit.
Try again. And again.
If it still doesn’t work, you can try uploading to DropBox or a similar service (make sure it’s without personal contact info) and sending your buyer the link.
There’s a workaround for that, though: your buyer can place another order for a smaller amount (for example, if the original order was for $100 and you wish to refund $30, the smaller order would be for $70), you deliver on that smaller order, the buyer accepts, and you cancel the bigger order, so your buyer basically gets a partial refund.
It’s far from ideal, of course, since the cancellation will harm your stats, plus the whole thing is a hassle, but it’s the only way to give a partial refund.