question

I did this but it made no change. The Phoenix inverter was a few versions behind. But the screens remain the same. I noticed that the one shed that was looking right, I found that the VE direct cable had fallen out :-(

After I put the cable back in, the values in all shed now read wrong, bugger

It's a calculated figure, and will rarely (if ever) show zero. There's issues making these calcs too, the first of which is that samplimg times for each of the inputs varies, so that's why it moves about a lot, and seems to exaggerate any instability in your system. Then it has to deal with system losses like standby power and conversion efficiencies. I've never seen the actual algorithms published (and never likely to), but it may actually make allowances for some kit like inverters in the calcs.

It's 'best-effort' and should be treated as such. If you really want to see what your wind turbine is doing without interference, grab another BMV or Smartshunt and allocate it as a turbine input.