This sounds more like a mechanical problem with the locomotive mechanisms than having anything to do with the decoder, even if they are the original DSD versions.
I have serveral locomotives into which DSD decoders were installed 'way back when' and none of them have exhibited this problem.
That's sort of backwards, usually decoders will act up when they get too hot. This might instead be a mechanical problem, or old caked on grease, which can get quite hard when left sitting. Once it warms up, the grease softens and everything runs smoother.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
A friend of mine has some engines that have the older DSD Soundtrax decoders that are wired in. These are all Proto engines that are giving a problem. They will stop and start at intermittent times until they "warm up" and then they run fine. Other engines run fine on this system and track. He uses easy DCC system. Any idea's??