failure to update graph created from averaging two other graphs

A graph created from the mean of two other graphs is not getting updated upon refresh.

To repeat:

(1) Load two graphs: Choose Species Arabidopsis thaliana, Genome A_thaliana_Jun_2009. Open Data Source Bioviz (DAS2) -> AtTile1R -> GSE9646 -> 10h_ABA -> GSM243689, GSM24690
(2) Zoom in somewhere (chr1 : 16,265,583 - 16,270,059 is good)
(3) Click Refresh data to load the two graphs
(4) Click Graph Adjuster, Select All, Operation -> Mean, observe a new graph appears that averages values from the two previously load graphs
(5) Zoom out to expose more of the region
(6) Click Refresh Data
(7) Observe that more data get loaded for the two graphs but the Mean graph does not get refreshed.

Note: Test other operations as well.