I've had the HO USRA 2-6-6-2 with Tsunami for a couple of years used maybe ten times, pulling 20 cars on level Club display oval layout for an hour or so at a time. After the first few sessions the rear engine began to lock up, and continues to do so, sometimes a couple of minutes after starting, sometimes 30 min. Lockup may occur in either direction, and I don't really know if its always on a curve or not. Sometimes, but not always, it will unlock by reversing direction. Mechanism seems perfectly free-running right up to lockup, and front engine continues to operate normally while rear is locked. I have lubricated the external stuff, rods, valve gear etc. Has anyone experienced similar lockups with this engine or with the H-4, which I assume has a similar mechanism?  If so, was the problem in the external stuff, or in the internal gear train?

Bob