I have a .vap showing Emporia power meter measurements which are taken every second, plotting 16 channels over 8 days. The fill-to-zero mode is used, and it looks like the fill part mishandles the reduced data. The data trace and filled data below are not consistent.
The script https://github.com/autoplot/dev/blob/master/bugs/sf/2425/demoBug2425.jy demos, and here's a screenshot.
This is fixed. The problem was that old code didn't use the reduced version of the data.