Small victory on Cisco ASA-SM in context mode and IPv6.

I have tried to run IPv6 on Cisco ASA-SM in context mode, but failed for quite a long time. IPv6 was down even everything seemed to be configured correctly.

> show ipv6 interface Vlan31
Vlan31 is up, line protocol is up
  IPv6 is stalled, link-local address is fe80::a0bc:f3ff:fe00:de [DUPLICATE] 
  Global unicast address(es):
    2001:db8:801:600::11, subnet is 2001:db8:801:600::10/126 [TENTATIVE]

Problem was caused by DUPLICATE link-local address. It seems that Cisco ASA-SM shares MAC address of interface on multiple contexts, that means, that there is a IPv6 address collision (because link-local address is created using MAC address) and IPv6 is malfuncioning. Setting IPv6 link-local address manually to ex. fe80::10 made IPv6 work on this link between ASA-SM and Cisco Catalyst 6800 switch/router like a charm.

> show ipv6 int Vlan31
Vlan31 is up, line protocol is up
  IPv6 is enabled, link-local address is fe80::10  
  Global unicast address(es):
    2001:db8:801:600::11, subnet is 2001:db8:801:600::10/126

UPDATE: I rolled step back to autoconfigured IPv6 link local address (configuration remains same as first config) and IPv6 keeps working! Strange, strange world of IPv6 on ASA-SM.

UPDATE2: ASA-SM returned to its old behavior and stopped working. Finally moved to manual settings.