Logging IMPORT and EXPORT on seperate feeds

Ok, I have a non-standard setup, my solar feeds in at one end of the house, and my grid connection is at the opposite end of the house. I have two EmonTx - one at each consumer unit:

SOLAR power is always 0 (at night) or a positive number.
GRID power is positive when we are drawing power from the grid, and negative when we are exporting power to the grid.

GRID + SOLAR = USE, works adequately

I’ve attempted to create two daily feeds for IMPORT kWh and EXPORT kWh, which is where I’m getting stuck. The IMPORT feed looks like the correct number (1.14kWh which is DailyPower - Solar Generated - correct)
However the EXPORT feed looks wrong - it just doesn’t add up. What am I doing wrong?

[Why all the "Reset to ZERO"s - without this the EXPORT feed freezes when there is no power exported. So at 7am, the export feed is stuck at the last value which was about 12 hours previous. So the idea is to keep updating the feed with 0s through the night, so the feed stays current.]