Okay, I tested the new Percy on track from a bulk box of Conductor Carl track that I have on hand, and it worked fine except for some pauses where it got briefly stuck on the short curved tracks. But, I then tried the new Percy on a similar configuration of Thomas Wooden Railway track, and then again on some Brio tracks, and it had the same problem, so I think this is down to a design flaw in the engines themselves. The new motorized Percy is larger in every dimension than the old one we have is, and I think the wheels are slightly too far apart to go smoothly around the short curves. The old Percy handled them with no problems.
The Thomas wooden train set hobby is wonderful and unique, and one that can span generations in the family! Just ask anyone who has a Wooden Thomas Train Set, or Brio Train tracks and they will tell you.