Boiler recalls

They obviously know about the problem but you may have to go through a few hoops to get it fixed. I'd book a call-out from Vaillant (hopefully there is an all-inclusive charge) and argue the toss afterwards. They won't respond to anything without an engineer's report anyway, and at least you get all the bits replaced at the same time

Yes Vaillant have changed the material of the seal, the ecoTEC models had the same problem and there was a product recall, the ecoMAX models also have the same problem but Vaillant don't admit it and never done a recall, your best bet would be to call Vaillant and argue with them. I remember reading a about someone who had a Vaillant boiler with a seal fault, Vaillant said the boiler was beyond economical repair and replaced the whole boiler!?

When was the product recall? I have an ecoTEC Pro 28 R1, which is around a year old, is this likely to have had the mod at manufacture?

Thanks

Yes most likely, the recall was for earlier 2005 models IIRC, call Vaillant just to be sure AND when it's serviced the seals have to be replaced if the engineer opens the burner.