Hello Steffen,
thank you very much for the help.
I got all three phones new in the original packing this month.
The VVX 310 I bought second hand. They were never used emergency replacements in a company.
For the VVX 410 (00:04:F2:6F:CE:01) I have an invoice from this month.
In the meantime also this phone dropped the registration, but this was the first time whereas the VVX 310 do this all the time, so that they are not usable at all.
I now made a paket trace between the FritzBox and one of the VVX 310 above.
There I used the original timing values of 3600 as you recommended.
It would be really great if you could have a short look at it.
Thank you very much :-)
