faulty engine chip query

[malcolmr]

I have an 00 gauge DCC layout with seven engines controlled by a Digitrax DCS 51 controller. One engine, a fairly new Bachmann 0 6 2
tank engine, has recently become faulty - when slowing and just before stopping, it suddenly speeds up for a few inches, slows and then stops as normal. I have tried several times to reset CVs to those recommended by Digitrax (CV followed by setting) for a shunter - 2/26, 6/38 and 5/64 and for a low speed engine - 2/26, 6/48 and 5/98 but the problem continues on all parts of the layout.
As the fault is specific to this engine I assume it is not a controller fault but the engine chip at fault or, is it me, who only has a basic knowledge of DCC matters? If any reader can offer a solution, can it be couched in simple language and have every step detailed. Thank you.

Kind regards
Malcolm Redgrave

[brian1951]

Turn off DC operation ( cv 29 ) and try loco again.

[Rog (RJ)]

What make and model of chip is it?

Some Bachmann decoders are well known for needing CVs 53 & 54 adjusting to avoid "jumpy" starts and stops.