Michael Hertel sent me a message and said he had found a problem with the newer revision of hl7Raw_ack. It seems I was not reversing sending and receiving application/facility (MSH.4.6) as I did with the older model. I tested it and he is correct. The problem has probably not surfaced before as very few HL7 ACK recipients even look at those fields. But for those that do, it is important.
I have uploaded a new copy of hl7Raw_ack.