This is not a faulty part per-se but possibly that these meters are more susceptible to dissolved air in the system.
This happened to me after octopus changed half of the radiators and forgot to put inhibitor back into the system (grabbed a bottle of x100 from toolstation and filled it via the magnetic filter).
Trystan covers this in more detail here - Kamstrup Multical 403 Erratic flow readings - #28 by TrystanLea
May be worth a read as it will help you explain what may be going on.