Whilst newer boilers might use less gas, their running costs seem to
offset any saving!

Not sure if anyone here can help, but I get lock-out and an E-128 error
that implies that there have been a dozen flame failures.

Symptoms are that the boiler fires up nicely, but I can see/hear the gas
rate is changing over time (undulating) and never ramps up to max, even
though CH water is cold.

Subsequently the boiler cycles between running, purging and relighting
such that the water temperature never gets above 50-60 degs.

All the menu accessible temperature sensors seem spot on, the ionising
electrode has been gently cleaned, though not with any abrasive.

Any ideas?