BCWP display

I'm doing some EV reporting and have a problem with BCWP display value. In the Gantt chart the BCWP column displays values fine and rolls up to the summary project level as it should. However, when I'm looking at a time series report it only displays the BCWP (and subsequent calculations of the SPI and CPI) for the lower level tasks, not the summary task (see images).

I've used this view/report before and the BCWP, SPI and CPI all displayed correctly for the summary level task, but now those values just will not display. I've removed/re-added the value from the report and that's made no difference.

Not sure there are a whole lot of things that can be used to affect this display so I'm quite lost. There only seems to be one BCWP column (unlike many cost and date fields) so I can't see how I could have picked a different column to display in the time series vs. the Gantt view. Anyone have any idea what's going on here? I'm sure it's something I've done, I just don't know what it is.