Zero Savings in AC Charging Totals

Gas Savings is correctly shown on individual drives:

and Total Gas Savings is correctly shown on the daily summary:

but Savings in the AC Charging Totals is always €0.00:

I tried rebuilding drive records, but that didn't help.

I have the following settings under Gas Savings:

Note setting Display Gas Savings As: The Difference Between Drive Cost And Gas Cost makes no difference.

Thanks.