Have you possibly set your DCC system to send 14 2peed-step commands to this locomotive address?
?
What DCC system (and what throttle) are you using?
I'm using JMRI with Sprog. Same effect if using Engine Driver or just on-screen throttle. I've not changed the speed steps, but I had this once before and had to program the decoder to 14 (as it was reading as 128) and then re-program it
to 128 and that worked fine. I've tried this using JMRI screens and using CVs directly and nothing improving.