I am experiencing challenges getting IPv4 over DS-lite to work. 
My ISP is Stadtwerke Flensburg (SWFL) who offers Fiber (Glasfaser) with Dual Stack where IPv6 should be the primary stack and IPv4 should work over DS-lite.

I have tried both with a X50-POE v1 and v2, and despite v1 runs a higher firmware version is seems v2 is more stable when it comes to establish a working IPv6 connection.

IPv6 setup:

PPOE

Non-address

Prefix delegation enabled 

DNS auto 

DHCPv6

Any other setup doesn't seem to work, and there is zero support from SWFL support as they only provide support in connection to their FRITZ!box router. 
 

IPv4 is set to DS-lite where I have tried both to get the AFTR Name automatically and manually via the AFTR Gateway I can find used in the FRITZ!Box. Here, I had the most success using an IPv6 address as it shortly gave a IPv4 adr (only for seconds) before my POE was thrown completely off. Using the FRITZ!Box visible FQDN doesn't seem to help. 
 

Currently, devices that seems not to support IPv4 are not functionally despite they are assigned an IPv4 address by the POE. 
 

Any advices?