IPv6 advertisements leaking across subnets

I’m not sure if this is expected behavior or not thanks to my limited experience with IPv6. I have RB493G units with RouterOS 5.12 deployed in my network each with an assortment of VLANs and bridges set up. I’ve had a /48 assigned from HE and set up each existing VLAN to have its own /64 subnet. After setting up all the routes and IPv6 pools and ND/advertisement settings, I’m finding that my Windows servers are picking up IPv6 addresses on all subnets instead of just the one for the VLAN they’re connected to, and using one of the bad ones as a default route:

For example:
2001:470:xxxx:1::/64 - servers (VLAN 2 on ether3)
2001:470:xxxx:1101::/64 - workstations (bridge)
2001:470:xxxx:1111::/64 - VoIP (VLAN 3 on ether3)

C:\Users\dkirkman>ipconfig

Windows IP Configuration


Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . :
   IPv6 Address. . . . . . . . . . . : 2001:470:xxxx:1:18b4:d20:337a:ea7e
   IPv6 Address. . . . . . . . . . . : 2001:470:xxxx:1101:18b4:d20:337a:ea7e
   IPv6 Address. . . . . . . . . . . : 2001:470:xxxx:1111:18b4:d20:337a:ea7e
   Link-local IPv6 Address . . . . . : fe80::18b4:d20:337a:ea7e%10
   IPv4 Address. . . . . . . . . . . : 172.16.10.2
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : fe80::20c:42ff:fea8:be17%10
                                       fe80::20c:42ff:fea8:be16%10
                                       172.16.10.254

This may be a Windows Server 2008 problem, since my Linux and Windows 2003 servers seem to be working correctly:

root@web1:~# ip -6 address show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 2001:470:xxxx:1:20c:29ff:fe2b:e4d2/64 scope global dynamic
       valid_lft 2591732sec preferred_lft 604532sec
    inet6 fe80::20c:29ff:fe2b:e4d2/64 scope link
       valid_lft forever preferred_lft forever



C:\Program Files\Support Tools>ipconfig

Windows IP Configuration


Ethernet adapter Local Area Connection 6:

   Connection-specific DNS Suffix  . :
   IP Address. . . . . . . . . . . . : 172.16.10.3
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   IP Address. . . . . . . . . . . . : 2001:470:xxxx:1:230:48ff:fe68:5b98
   IP Address. . . . . . . . . . . . : fe80::230:48ff:fe68:5b98%4
   Default Gateway . . . . . . . . . : 172.16.10.254
                                       fe80::20c:42ff:fea8:be17%4

Anyone have any ideas how to fix this?

Please post your /ipv6 address print
/ipv6 nd print
and /ipv6 nd prefix print