pfSense

How to reproduce:
1) Check the link-local address on the interface:

ether 12:4b:e1:60:76:e9
inet6 fe80::104b:e1ff:fe60:76e9%vtnet2 prefixlen 64 scopeid 0x3

2) Enable MAC spoofing (MAC: 00:90:0b:18:ac:ca):

ether 00:90:0b:18:ac:ca
hwaddr 12:4b:e1:60:76:e9
inet6 fe80::290:bff:fe18:acca%vtnet2 prefixlen 64 scopeid 0x3

3) Disable MAC spoofing:

ether 12:4b:e1:60:76:e9
inet6 fe80::290:bff:fe18:acca%vtnet2 prefixlen 64 scopeid 0x3

Link-local address is not updated

Workaround - reboot

it seems "ifdisabled" option should be used in interface_bring_down() and "-ifdisabled" in interface_configure() to re-generate link-local address, see ifconfig(8):

     ifdisabled
         Set a flag    to disable all of IPv6 network communications on the
         specified interface.  Note    that if    there are already configured
         IPv6 addresses on that interface, all of them are marked as
         "tentative" and DAD will be performed when    this flag is cleared.

     -ifdisabled
         Clear a flag ifdisabled.  When this flag is cleared and
         auto_linklocal flag is enabled, automatic configuration of    a
         link-local    address    is performed.

may be related to #12790