Apple Airport and IPv6

I have my Apple Airport router set to "link locally" for iPv6.  It stopped having to reset the modem and router every day in order to restore connectivity HOWEVER lately I am beginning to have intermittent dropoff where I lose connectivity for a couple of minutes and then get it back.  Sometimes if I reboot my Mac, that does the trick.

Why can't I get reliable service from Cox???  I have the very latest modem and I have the recommended IPv6 settings on my Apple router.  Has something changed on Cox's end????

I am in Louisiana - Metairie New Orleans area