I went and looked at the NCE group info. I’m afraid that I don’t think belaboring the point about whether it is a ProCab or a PowerCab gets anyone anywhere.
From what I have read, you are using the ProCab to operate your locos, and you don’t want to use the recall function. If I may make a suggestion, see if you can borrow one of the non-programming throttles. Make sure you borrow one with an encoder, not a rheostat, Try that and see if you still have the “problem”.
Well I’m working with Matt at ESU now. I pointed out something else that I hadn’t thought about to him.
I have two other locos with Loksounds. SD70M’s. And looking at the cards in the SD70’s and the ones in the new C44 locos, they look identical. Up to the point of having the same ink pen markings on the shrink wrap.
What is weird is I don’t have this problem with the SD70’s! So it’s a setting. I think it is fixable or adjustable. So tonight I’m going to copy the settings from my SD70M and the new C44-9W’s and Matt is going to compare which of the CV’s are different and which could be causing the problems.
Please be sure to report back. The Select decoder that I was describing with a similar issue was for a RS3.
I will most certainly keep everyone posted. 
5150WS6:
Did you ever get this solved?
Maxman,
I did not. After much talking with Matt at Loksound it seems it’s something they are working on.
The only solution was if I used the recall button after programming both locos into it. Then it will allow me to switch between locos without one shutting off.
This was a bit ago and I haven’t checked with Matt to see if it has been updated or not as of yet.
Mike
There is I believe some sort of configuration in NCE as to which functions are refreshed when a loco is active but not the selected loco - as you are doing. I do not have this same issue switching back and forth between locos with my Digitrax equipment, because the loco remains active unless you specifically clear it from the command station (the dispatch proceedure you see mentioned for Digitrax). Selecting an already active loco on the throttle merely reconnects the command station ‘slot’ holding that loco to your throttle, allowing you to take control. It would appear that with NCE, selecting the loco (not using recall) sets it up in the command station as a fresh loco even though it was previous selected. Using recall returns it to the previous state which is why that works for you.
Another reason why I don’t like ‘recall’ being an item on DCC system comparisons. Digitrax has a recall stack, but it’s not needed for the same purpose as it is on say NCE.
–Randy
I know this is a super old post (sorry about resurecting the dead) but I am wondering if anyone here has ever figured this out. I have the exact same thing happening with the same loco as the OP. it is the Kato c44-9w
I wonder if it isn’t a CV setting on the decoders that causes the engine sounds go into idle mode when the decoder reads the engine as no longer being addressed by the DCC system?