Ah, I just noticed you use an EmonESP directly from the heatpump to EmonCMS. Limited scope to debug that I fear.
Is that an EmonESP log or Emoncms log (I do not use either)?
If EmonESP, it shows that the data is not being generated at a regular interval. @glyn.hudson or @TrystanLea will be your best help.
That is the success of the sent messages. If the EmonESP is not generating the message, it will not be measured as a failure.
No it should be regular. My personal suspicion is the ESP module. I have had countless problems with ESPs and Wi-Fi over that last few weeks. My conclusion is that the current Wi-Fi implementation for ESPs is unreliable. You can find a fair bit of chat on this out there.