Alco S2 - start speed difference based on 1 or 2 digit address

[West Bound]

Using digitrax system with a Sprog interface for a JMRI programer.
If I assign a single digit address of 1 through 9 loco will start to move at speed step 1. Any 2 digit address will delay start movement until speed step 12. The speed at step 12 is not as fast as step 12 with a single address but equal to step 4 using single digit address. I've done a comparison of all the CVs of both addresses and nothing other than the address has changed.
The easy fix would be to assign a single digit address. I have 20 other locos all with 2 digit addresses so it will be confusing to have one engine with a single digit address.
Has anyone else experienced this, and if so, how did you resolve it?
Thanks, John West

[West Bound]

No, Cincinnati area

Is this John West of northern Michigan?

Jon

[bapguy]

 What decoder brand? Same one in each? Sounds like 1 might be running on 28 speed steps the other on 128. Look in the front of your system manual for decoder status. Not all decoders support 128 speed steps.       Joe

[West Bound]

There is only 1 loco doing this. The S2, Bachmann sound value 128 steps. I have 2 other sound value steam locos no issues along with 18 or so other brands.