I remember seeing a post on this once, but cannot recall where it was. I recently retired a couple of hosts. They still appear in BAM! though, even I deleted them quite a while ago at the projects where BAM! says they have credits.
I'm pretty sure this in not a BAM! issue but of the projects themselves. I'm interested however if a fix or some 'repairtrick' on this issue is known/available/being made.

FYI I manage 5 hosts but have 17 in total reported in BAM. Some sre 100% the mentioned retired ones, some are duplicates coming from projects where I retired these hosts.

TIA,

WimTea