Graph dips

Nosing at some of the graphs on
What’s the cause of the dips with the flow and return temps during the DHW heating?
Is the heat pump turning off for a few minutes?

That looks like a defrost cycle, if you zoom in on the periods where the heat pump appears to be off, you will see the return temp higher than the flow and an increasing electrical power with no heat output.
Prolonged low outside temps and increased load on the DHW cycle can cause it to defrost mid cycle.