As a follow up and closure, I gave the switcher some more run time yesterday. First, a couple of laps around at medium speed in the opposite direction, just to verify that I didn't transfer the bind from one side to the other when I did all the poking and prodding. Then back to the counterclockwise direction with all the right hand turns. Two laps at speed step 8 required almost 35 minutes, and no stalling or hesitation.
Whatever was in there (as Randy noted - potential ballast or similar) is gone and I consider this a reliable steamer again.
Thanks for your input!
RLS