With a MIGS API gateway, if you see this returned error back to your website...

"E5432-05270118: Internal Error : Failed to perform transaction via payment engine"

and you then jump into the Merchant console and run the same credit card details you will see:

"There are too many concurrent transactions being processed against this merchant, please try again"

The reason for this error is not very clear - but its coming from MasterCard payment engine.

It may be casue by trying the same credit card too many times.

If you wait a while and try again - the transaction will go through.