I have tried adjusting the lengths of these notes, but they still turn out wrongly in the Notation and Leadsheet views once (re)generation has been requested.

The onset and duration of these notes is:

beat 1, tick 0
beat 1, tick 80
beat 2, tick 40
beat 3, tick 0
beat 3. tick 80
beat 4, tick 40

and all durations are set at 64 ticks. I've tried adjusting them all by stages up to 80 ticks, but this makes no difference.

As the timings all seem to be arithmetically accurate, I'm not sure where to go from here.

In case there's something very strange about this (admittedly old) file, I'll try creating an entirely new song in BIAB 2013 and see if this behaves in the same way.

Michael