I have a HO K4 4-6-2 Pacific Loco w/sound & DCC which I purchased about 6 or 8 years ago.  It has very few hours on it... probably less that 5.   Initially it ran fine, however, now I can not get it up to speed.  It starts off great and will increase speed up to about speed step 7 or 8 (out of 28) and it will not go any faster.  As I increase the throttle to speed step 10 or 15 or 20 or even 28 the chuff sound will pick up appropriately, however, the loco will not pick up speed.  I have tried everything including setting the cv's all back to factory settings.  All thoughts?

Thanks,
Johnny D