I’ve seen the same behaviour for my system (Derby, GSHP) - typically shows ‘COP 30 mins’ as 0.00 but occasionally an implausibly high figure. I’d wondered if this was because I only post updates to the Inputs / Feeds every 2 minutes but looks like your data is feeding much more frequently than that Rachel, so must be something else going on.
Looks like the code that drives this view is app/apps/OpenEnergyMonitor/myheatpump/myheatpump.js at master · emoncms/app · GitHub