DPC3939B cable modem changed the /64 subnets from ::13e0:and ::13e1 to ::13c0 and ::13c1
I have DPC3939B cable modem and have ben sucessfully using ipv6 for some time. The cable modem, for the past 2 years (or more) has been assigning two subnets form our zzzz:xxxx:yyyy:1300/56 prefix deligation. Those subnets have been zzzz:xxxx:yyyy:13e0/64 and zzzz:xxxx:yyyy:13e1/64.
After a router reboot (not modem reboot, but our internal router), the cable modem is now assigning 13c0/64 and 13c1/64.
This has messed up all of our staticly assigned IP adresses to various servers and subsequent DNS assignments. Now I am faced with many hours of work to correct the issue.
How can I get my cable modem to go back to assigning the 13e0/64 and 13e1/64 subnets to my router?