OpenWRT 18.06.5-18.06.7 and IPv6 part 2

This is continuation this topic OpenWRT 18.06.5-18.06.7 and IPv6
I detect , what if ping small 1-7 ms - IPv6 not connect. But if ping 13-15 ms to last mile - IPv6 - always connect if use this method :
20 3 * * * ifdown wan; sleep 15; ifup wan; sleep 5; ifup wan
As I can add ping time to 10-15 ms ?
Thanks.

Why if I create some onces reconnect - IPv6 will be recived ? As do this so , that would IPv6 will be always recived ?

So no fix for this problem ?
I posted this in another topic.