I purchased this switch about a month ago. It's been working fine so far, until I just recently started setting up VLANs on my network.

The IPv4 side of things works fine as far as I can tell.

When I connect a new device on the VLAN, it'll get 2 IPv6s at first (regular + temporary). IPv6 works fine at that point. I've tested it with IPv6-test-sites.

However, a few seconds later, the test-sites stop working altogether. All ipv6-tests fail. The addresses timeout.
When I go back to my network-device settings, I notice that instead of the original two, I now have four IPv6 addresses assigned. It remains at 4 from then on. And IPv6 connections fail permanently.
When I disable/re-enable the network interface on my VLAN-devices, I'm back to two IPv6, but then a few seconds later, same thing happens.

Everything works fine on the LAN networks. But all basically VLANs are unusable because of thse IP leaks.