I did notice a bug in the drop-model, but not one that explanes exactly what you describe. The wrapper of cbApplyMove does demotion and testing for Pawn capture in the wrong order (lines 142 and 143). With as consequence that capturing a Tokin decreases the Pawn count for the file where it happens. So it should not matter in which file you promoted, but depend on where the Tokin was captured. As the Pawn count is updated incrementally, the error would persist for the rest of the game.
I did notice a bug in the drop-model, but not one that explanes exactly what you describe. The wrapper of cbApplyMove does demotion and testing for Pawn capture in the wrong order (lines 142 and 143). With as consequence that capturing a Tokin decreases the Pawn count for the file where it happens. So it should not matter in which file you promoted, but depend on where the Tokin was captured. As the Pawn count is updated incrementally, the error would persist for the rest of the game.