Just a passing thought: is the diaper a disposable, of the ultra-thin variety?
and could the grit be from the diaper (the super absorbant agent that later
feels like jelly beads when saturated), getting mixed with the stool and just
not swelling/responding because there is not enough fluid to cause the
swelling/softening? I've seen this sand-like grit clinging to the interior
surface of off-brand disposable diapers. Again, just a thought.

Jeanine Klaus, MS, IBCLC
Oakville, Ontario