IPv6 neighbors are always reserved

When the system has been running for a period of time, you can view IPv6 Neighbours or ip -6 nei show command through the LUCI WEB interface (/cgi-bin/luci/admin/status/routes) to view many IPv6 neighbor information, even if the nud STATE FAILED record is always It is reserved, and it is invalid to delete with the ip -6 nei del *** command. After using the ip -6 nei flush *** command, the LUCI WEB interface (/cgi-bin/luci/admin/status/routes) is used to view the IPv6 Neighbours display position Empty, how can I clean up these invalid IPv6 neighbor records?