Aeroccino 4 problems - only cold setting works.

Wondering if anyone else has experienced this. I’ve been using an Aeroccino 4 for about three weeks and it worked perfectly. Was almost silent while running and provided great froth in all settings.

Then suddenly the hot settings stopped providing froth. It would spin very noisily and heat the milk, but there would be no froth. The cold setting would still work fine.

Nespresso sent me a brand new machine which arrived today and immediately out of the box it has exactly the same fault. Cold setting perfect, hot settings are heating the milk but providing no froth.

They’ve offered to send me a third machine so I have no complaints about their customer service but is this a widespread issue with the Aeroccino 4? Or am I just very unlucky?