The following simulation illustrates a Hosted Payment Form Load error during Pay Invoices by Email where a PayPal Connection is primary and a Braintree Connection is the fallback. 

Send a Pay by Email invitation containing invoices where the Customer Reference is ERR02.  Click Pay Now and select the invoices to pay.

Now, when the payment screen loads you will experience a simulated timeout of the primary connection.

Once the primary payment page times out the fallback payment page will display.  Process the payment. 

Now, you can see the payment in the fallback account, not the primary.

To finish the simulation run the RQ6704218 report to retrieve the payment from the PayCloud and record it in JDEdwards.  Make sure the processing option is set to use the primary connection.