PayPal rejecting parts orders payments

[gcharlesc]

Does anyone know why PayPal sometimes places parts orders in pending status and then cancels them?  Sent an email to the parts guy with the question and got no response.  Sent an email to PayPal with the question and they replied that they couldn't divulge their review and appoval process.  Happens every second or third time, end up having to pay with a credit card.