retail pro is hardcoded to timeout on credit card and debit transactions after 120 second. if the pinpad or signature capture unit is set in the Shift 4 UTG tune up to timeout before the 120 second (we were using 90 seconds), retail pro will get a timeout message, but shift 4 might still process the card.
at 90 seconds, the signature capture unit times out. at this point it will reset ad start to try running the transaction again. for 30 seconds it is still talking to retail pro because retail pro hasn’t yet timed out. once retail pro times out, the signature capture unit is working for 60 seconds independent of rpro, and using shift 4 alone. if someone is slow on the transaction, (busy talking, not understanding the technology being used, etc.) this could occur.
to correct, change the timeout function in the Shift 4 UTG to 120 seconds. by simultaneously timing out with rpro, it will not reset the pinpad to try again, because retail pro is not longer asking for authorization after 120 seconds.