The following simulation illustrates a Hosted Payment Process Result error during order entry where a Braintree Connection is primary and a PayPal Connection is the fallback. 

Enter the order header making sure to use ERR03 in the Customer PO field and the payment instrument designated for credit card. 

Enter order details and advance to the payment screen. Before you press Pay with New Card make sure your total to authorize equals $3000.  Press Authorize with New Card.

Enter the payment information into the primary payment form and process the payment.

Now, the error is simulated and you get the notification to Retry.

Click retry and the fallback payment form will be presented. Remember that since Paypal is the fallback in this scenario anything over $1000 will decline.  Therefore, this is the end of this simulation.