Aha. This may then be related to 200% Watering because of .9999 precip today if the one time a day this level was computed fell in the same window where, according to this bug linked to, I ended up with a 200% watering there. I see a few day with 3 WL samples taken in that window where WL=200 if I retrieve using the URL provided.
So, I’ll look again in a week, now that the linked bug supposedly has been fixed and see if the problem goes away.