[A5500] DHCPv6 snooping bug?

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On HP A5500-EI with R2220p02 I am recently experiencing problems with DHCPv6 snooping. Some clients (even on the same port of the switch, i.e. with a small unmanaged mini-switch) get either:

- IPv6 address from the server, get the default gateway (FE80) of the switch, but simply cannot ping anything, except the default gateway.

- IPv6 address from the server, but not the deault gateway of the switch, which also result in no IPv6 connectivity

- get everything above and have instantly full connectivity.

• Btw, with DHCPv6 snooping enabled, I do not see any client with "display ipv6 dhcp snooping user-binding dynamic" in this situation, not even the once having full connectivity.
• releasing and renewing the IPv6 address don´t work, clearing any entries on the switch doesn´t work, either. Booting switch, clients, nothing helps so far.
• But when I disable DHCPv6 snooping (globally), everything works for all.

(Not to mention that all nice SAVI features don´t work as expected because of this issue)

Am I the only person with that problem?