kWh per day feed incorrect and virtual feed not working

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I’m converting an input from a meter that counts its kWh incremental into a feed that should do kWh_per_day, but the values are identical for the total kWh increased, since the creation of the feed. So, value for day 1 = day 10 = total kWh since creation of the feed (when I visualise the feed for kWh_per_day). Is this a known bug? Point is that graphing it as a bar chart from the kWh split per day, is not a solution for me.
Next is that I have a Virtual feed which should distract measured subloads (in kWh_per_day) from the total consumption (in kWh_per_day). I’ve tried both + (and -) feed or + (and -) source feed in the input to create such virtual feed. But when visualizing the virtual feed, it shows nothing, not even the axes of the graph. Just the timeslicer (Y/M/D /Y /M /D…). Am I missing something?