What temperature is the tank heating from? COP is best when tank starts from cold. Need to be wary of starting temps when comparing DHW runs, as they may not be as equivalent as you think.
The start of today’s run @ 14:10, the return goes way higher than flow, suggesting that it was taking (borrowing) heat from the cylinder before the heat pump started up. The measured heat is negative for the first couple minutes as a result.
This morning’s DHW cycle @ 8:20 faired much better, yielding a COP of 3.94, which is pretty decent, though mostly thanks the slug of free heat at the end (though that may have gone to your radiators). Even the middle section averages a COP of 3, which is still good. I’d guess that the tank was colder this time.
That second DHW reheat in the afternoon was probably unnecessary, and could have been skipped entirely. Try increasing the threshold for how much the tank temperature can drop before it will reheat it (I’ve mine set to 20 degrees).