Hello,
From 8006:6c8e:a82:283f:a82:28f7:50:ab77 to ff02::1, proto 58
That would be ICMPv6, equivalent to IPv4 ARP. It could be from any IPv6-enabled host/PC/printer etc. likely misconfigured because 8000::/3 space is reserved
https://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml
Do You use IPv6 on this ISG2K at all? If not I suggest You disable it altogether
https://kb.juniper.net/InfoCenter/index?page=content&id=KB15692
HTH
Thx
Alex