Pivot Table Summaries Getting #REF Error?

sarahsfocused

I have a few pivot tables set to update weekly, and seem to be refreshing the actual numbers just fine. However, I have some summary functions set up that have totally stopped working, instead giving a #REF Error:

I'm a little surprised, as it worked perfectly (with real cell references, not #REFs) when I originally set it up, and the pivot itself has no trouble populating updated data. It seems that when the pivot refreshed, though, my summary functions lost all valid references. Is there a way to keep this from happening? I would like to keep the pivots current, and the calculations based on it also current. Thanks for any advice!