As i already wrote in the CLAT Thread:
Please don’t get me wrong, CLAT seems to be a very good alternative to “real” IPv4, the implementation of CLAT in Sailfish is very important and needs to be done.
But CLAT cannot repair an incorrect connection establishment (IPv6 only although the MNO provides ipv4) or an incorrect switching process between ipv6 only mobile data and IPv4 only WLAN.