As mentioned above. when traveling from the points toward the frog, the MTH caboose roller is dropping off the end of the short side stub rail of the 11 degree Ross spring wye, dipping into a short void and tripping on the diverging rail, derailing and shorting and abruptly uncoupling from the train. This occurs at the spot of the yellow thumb tack in photo below.
It may be good to lengthen the side stub rail about 9/16" and install a curved inward dipping pin to clear diverging flanges when the other route is used.
For right now my thought is to slip in a piece of plastic struct to effectively compress the roller spring raising the roller from any contact.
Meanwhile the MTH cabeese are removed from service.
Ross suggested to remove the roller. mount it in a drill chuck and file a taper on each end.
How is the roller removed without destroying anything?
Based on actual experience, which is best approach? Thank you for your comments.