The outside dancers did a Pass Thru but moved laterally one space (so there were two spaces between them and the center dancers).
If I eliminate the Triple Box on the last Pass Thru, the dancers Pass Thru as expected.
Is this indicative of some subtlety on triple boxes that I don't know about? Or is it a bug?
The problem is that more than one snapshot record 'matched' the phantom position. Since the program couldn't determine which snapshot record was correct, it used the first one that it encountered.
Pass Thru can be done from either Facing Dancers or a Right-Hand Mini-Wave. Since phantoms are, by definition, facing in whatever direction is necessary to do the next call, the program incorrectly used the Right-Hand Mini-Wave version of Pass Thru since that was the first record it encountered when searching the snapshot database.
Because Pass Thru from a Right-Hand Mini-Wave is not the 'normal' starting position for Pass Thru, this information needs to be conveyed to the program. This is done by changing the 'Priority' field of the snapshot record to something other than 'Normal'. The program will then select the Facing Dancer version of Pass Thru over the R-H Mini-Wave version whenever it has a choice.
To fix this particular problem:
The problem should go away.
This particular instance of this problem has been fixed in the my master snapshot database.