I have worked for Gapbuster for about 1 year now. They pay when they say and direct deposit which is great. If you have a problem it is very difficult to get a response that day. As with the rest of you I'm trying to input information within their deadlines but they have never responded until the next day. I have input quite a few shops late because of this and I do not know how this impacts on my rating because we are not privy to that.
I too have been contacted to complete 'emergency' shops with a nice bonus included, all agreed to during the phone call.
The problem I've had with uploading receipts is the size and I usually go with the lowest quality, that usually rectifies the situation. Another try would be to cut off or fold over unimportant information on the receipt such as: Thank You for Shopping!!, etc.
One final note that I disagree with any Mystery Shop Co. is sending them a copy of EVERY receipt. I feel if there is a problem than ask for the receipt, otherwise I am wasting a lot of my time preparing and sending receipts. Another solution would be random receipts which I would accept also. If they suspect someone of not completing or falsifying information than request them to submit all receipts as part of a probation.