Most everyone is having success with this module - as far as I can tell. It it being used in production at numerous high volume sites. That particular result you are seeing is part of "duplicate transaction" handling. QBMS will not make the second charge if it has already run a charge for the exact same amount in a short period of time (to prevent double clicks from inadvertently creating a second submission).

To diagnose your particular issue - you need to give more data. Are you production (not testing)? Are these in fact same charges being submitted quickly to test? Or is this happening for any amount and every time?

That message/result occurs when, upon submission of a cc transaction, a search of existing orders in Zen show that another order has the SAME TransactionID for the charge. That is what tells the module that QBMS already processed that charge - and has returned the same transaction ID and will not process again.