Cumulative sum on secondary axis not resetting to zero?!

[Wolly]

I have a cumulative measure of return that calculates correctly and displays correctly in isolation--when  I place the measure in a single line graph, I can vary the starting date via slicer, and the curve always begins from a zero value.

As soon as I place that same measure on a secondary Y axis, its calculation no longer begins at a zero base.  It displays as if it had calculating a cumulative value starting from the earliest start date available yet the graph displays data bounded by the same slicer.

See pic below.

All help appreciated.Line graph is the same calculation

[Ashish_Mathur]

Hi,

Share the download link of the PBI file.

[Wolly]

It's become a pretty big pbi file so need to figure out how best to isolate the issue to upload.  I was hoping there might be a quick and perhaps obvious assessment of what might be going on.