Result of Math Expression is missing dimension value if one of the metric it is calculated from is missing it

Hello everyone!

I’m trying to create a dashboard with math expression calculated from several queries - Geneva metrics.
I have 5 Geneva metrics (A, B, C, D, E). All of them have the dimension “region” with 3 possible values.
For all of these metrics, I first perform a Reduce operation to calculate sum for a given time range with Mode “Replace Non-numeric values” with 0.
Then I perform Math expression :
(A_Sum + B_Sum) / (A_Sum + B_Sum + C_Sum + D_Sum + E_Sum).

First problem I have, is that metrics C, D and E not always have values for all regions (this is expected). And if I have a metric that has value only in 2 (out of 3) regions, then the whole expression will have in result value only for these 2 regions, even if the rest of the metrics have values for all 3 regions.
My expectation would be, that values for the missing region would fill with 0 and the whole expression would have values for all 3 regions.

Version: Grafana v9.5.19
Data source: Geneva