Issue with historic BCWP

Hi all,

Apologies in advance if I've posted in the wrong thread and also if my explanation of my issue isn't that clear, I am fairly new to planning/P6!

I'm using Primavera P6 v8.2 and have noticed that historic BCWP seems to be moving from previous months, to the current month, even when no progress has been recognised that month.

I have the original baseline plan set as the primary baseline for the forecasted plan. The forescasted plan is the one I make my progress updates on. I am having an issue with activities which are in progress. Say for example I have an activity which is 50% complete, with a cumulative BCWP of £45k (£15k in July,£15k in August and £15k in September). Say in this example there was no progress in October, so the cumulative BCWP is still £45k at the end of October, when I move the data date to the beginning of the next reporting period (beginning of November), P6 is taking a slice of all previous months BCWP, so in this example from July, August and September and putting it in October, distorting the historical BCWP (cumulative remains the same at £45k). 

Now, I'm assuming there is a setting somewhere, that I have accidently changed that is making this happen, but I can't figure out what it is and how to stop it!

Any suggestions would be greatly appreciated.

Thanks,

Ash