without having looked at code (always EFATAL) you would hope that a
zero driftfile was a special case, and did some kind of 'average over
<n> x initial samples' interpolation to get an initial approximation at
least close to the right side of the asymptote..

surely dave mills would have DTRT when initializing from zero, as
distinct from cached state?

Ie, if the driftfile is predictably wrong, because you changed
timesource, I can't see how its ever right to keep it..

-G