Yes, exactly, it does sound like a refrigerant control issue (LEV or EEV as you say). On the Ecodan you can get ‘running information’ on the controller screen. this gives all sorts of ‘live’ values including all temperature sensors, the compressor speed, fan speed LEV position , water flow rate etc. The LEV positions can be observed, but control is automatic and not hackable. Mu hunch is that the sampling rate is not quick enough. Most of the time the 20 second (or whatever it is) sampling might be enough, but in certain conditions it could ‘hunt’, i.e. overreact and start oscilating. I’m guessing they need to sample for LEV control at twice the speed.