While investigating this issue (https://redmine.pfsense.org/issues/12079) on my system, I came accross the following LOR which looks very similar to the one that was patched but for IPv6 multicast.

This is systematically reported during the boot but as not caused a panic yet (contrary to the IPv4 equivalent LOR), maybe because I don't have any IPv6 multicast traffic on my network.

lock order reversal: (sleepable after non-sleepable)
 1st 0xffffffff8243d2d8 IPv6 multicast interfaces (IPv6 multicast interfaces, sleep mutex) @ /root/pfsense_project/FreeBSD-src
/sys/netinet6/ip6_mroute.c:679
 2nd 0xfffff8000172a978 iflib ctx lock (iflib ctx lock, sx) @ /root/pfsense_project/FreeBSD-src/sys/net/iflib.c:4340
lock order IPv6 multicast interfaces -> iflib ctx lock attempted at:
#0 0xffffffff80cf8c0c at witness_checkorder+0xbcc
#1 0xffffffff80c980e3 at _sx_xlock+0x63
#2 0xffffffff80dec89a at iflib_if_ioctl+0x2da
#3 0xffffffff80dba87e at if_setflag+0xde
#4 0xffffffff80f5700c at X_ip6_mrouter_set+0xbac
#5 0xffffffff80d31297 at sosetopt+0xf7
#6 0xffffffff80d361ad at kern_setsockopt+0xad
#7 0xffffffff80d360f4 at sys_setsockopt+0x24
#8 0xffffffff8125661e at amd64_syscall+0x12e
#9 0xffffffff81228c6b at fast_syscall_common+0xf8