You have to go to forum.vodafone.de:

1. State stat the error also occurs with the Vodafone router.

2. that you already have done a factory reset of the Vodafone router.

3. that you already have turned your Vodafone router off for 24 hours and it didn't fix the error.

4. that you already talked to the hotline multiple times.

After that you have to pray that someone with the same problem comes along and endorse your problem. Like, "I have the same problem since...". This sometimes conjures a Vodafone guy who tells you he has informed the technicians. Than you have won and within less than a day the error is gone.

I was six month without IPv6 even though the error message was clear. The forum route finally worked.