Any row edit that affects a field in the index expression can cause a cdx size increase- even if the field is replaced with itself iow does not change. The old gather/scatter memvar method of editing data could cause this, as can any VFP event that massages the content of a control with datasource in the underlying table.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
