Foris shows connection test ipv6 error, even though ipv6 works just fine

I’ve created 6in4 ipv6 tunnel, it seems to work fine. The page on a client shows 10/10. But in Foris “Test Connection” button gives both “IPv6 connectivity: Error” and “IPv6 gateway connectivity: Error”.

What exactly is Foris testing? From Turis command line I can do without problems e.g. ping6 or tracerote6