People don’t live in shared dwelling residences because they thought they’d really enjoy sharing walls…

Exactly this. A detailed log and evidence is important.

Also, talk to your other neighbours and see if they have, or would report it.

As it is, resident B has 2 noise complaints in 8 months from resident A. Without evidence of all the rest of it, this fits all sorts of scenarios. People make malicious complaints all the time and the authorities (rightfully) shouldn’t just take your word for it that there’s a long history.

Always have receipts