And that was it! Removed the affected locos from a consist and now they behave as expected. Using a Deek-Robot motor shield without problem....
I did have two of the test engines in consist mode on another layout with an NCE system. I will see about that. But I had multiple locos for...
Got a functional DCC++ Arduino setup that has worked in the past. Currently no throttle launched has any effect of any kind on a selected loco....