I found what I did that created the errors.
Trainclass has 2 fields DispOrder (N 10.2) Train_class (A25)
TrainSubClass has 2 fields Train_class A25, Train_SubClass A50 record
TrainSubClass.Train_class relates to TrainClass.TrainClass

When I first started this, I did not include the field DispOrder, and everything worked OK. Then I wanted to the display order in the selection list to NOT be alphabetical. So I added the Field DispOrder and changed the TrainClass. index 1 to be ordered by DispOrder, Train_class.

This one change created the following errors
1. Cannot refind record
2. When entering the "child field "(TrainSubClass.Train_SubClass) the linking field would be erased.