Would you think this is a problem?

[user 130681]

Unless they ship their products without testing them at all, it shows their electrical installation is utterly unsafe. Dangerous people in dangerous premises...

Chinesium amplifier from a Chinesium supplier. Need I say more. Not sure how Trading Standards could take them to task, they seel people buy and because they sell cheap, the buyer takes a risk. I can say though that after my intervention with PayPal and Fleabay, on the customers behalf, they are no longer a registered seller with Fleabay.
No fault would be detected if the household mains was not protected with a GCFI/RCD unit. Earth and Neutral come from the same point after all.

AFCI units are still very expensive and the tollerances are improving by design.
An RCD/GCFI is sufficient I think.