Arris SB6141 and SB8200 DHCP issues

I'm having issues with my Arris cable modems. I started seeing this problem with my old SB6141, and I thought it might be a defect in the modem, but since upgrading to an SB8200, the problem is the same.

If I connect to the modem directly with a computer, I don't have any problem. But when I connect a router, I don't seem to get a valid WAN address from DHCP. I've seen this on 4 different routers: ASUS RT-N66U, 2 Linksys WRT54GS (one running stock firmware, the other running DD-WRT), and a Netgear R6400v2 running DD-WRT.

I gather that others have had similar issues which were resolved by a reprovisioning signal. Could I request the same?

Thanks,

Phil