No v6 after updating dynamic endpoint address

[Apcentre29]

   I am using dynamic IPv4. I successfully create a tunnel, and it usually works. But. After ipv4 change, I update it by https://USERNAME:PASSWORD@ipv4.tunnelbroker.net/ipv4_end.php?tid=TUNNELID and as a result I have NO ipv6 connection, according to lot of tests. Obviously I check endpoint address on my tunnel details page, it is correct. And no ipv6.
   As a temporal solution I get a new ipv4 address, use link above, then get messages "OK: Tunnel endpoint updated to: <actual ip>" and immediately " ERROR: This tunnel is already associated with this IP address. Plesae try to limit your updates to IP changes." But tunnel begins to work.
What might cause this problem and how to fix it?

[snarked]

Did you update the IPv4 address on your local device where the tunnel is terminated?

I note that some devices (e.g. the DIR-615) need the IPv4 address manually updated in its tunnel configuration.

[Apcentre29]

Of course. Problem usually appears when I turn off and after a while turn on pc and router. By the way, this issue happens not always: half an hour ago I turned on devices, I used that link and tunnel began to work as it should. Then I restarted router for test, updated ip again and everything now is working fine.
But, for example, yesterday I got not working tunnel after same doing.