The no-route report named the destination of the first unrouted packet
the process ever saw: the field was set while the window was empty and
never rewritten. A hub's own MLD noise (ff02::16) arrives early and
usually wins that race, so every later window blamed it -- including the
windows made of a peer's downlink being discarded, which is how a lost
registration stayed invisible in the log.
Set the window's destination when the window opens, and clear it with the
window, so each report names the miss it describes.