RIPE Atlas Probe - Poor Availability

I have a RIPE Atlas Probe (http://atlas.ripe.net) plugged directly into Comcast's DCP3941B router - it cannot maintain a connection to "home base" for more than a couple of hours.  See: https://atlas.ripe.net/probes/24971/#!tab-network

For comparison, Centurylink DSL (same site): https://atlas.ripe.net/probes/22802/#!tab-network

Note that Centurylink DSL is significantly more available than Comcast, and also that I might go days - sometimes months - on Centurylink without the RIPE probe getting disconnected, but making it to two hours on Comcast is the exception.

Does anyone else have an Atlas probe on Comcast that has IPv6 enabled?  If you do, and you have static IPs, do you see the same issue?  If you don't, can you let me know what modem I need to ask Comcast for?

If I enable IPv6 on a computer connected to the modem, browsing will sometimes hang randomly because the modem tears down state for some IPv6 connection between Google or Facebook's ad networks and my computer, and because no RST packet is sent, the browser has to time out before it knows that the connection is dead.  I suspect even when the IPv6 firewall is "disabled" that the modem is still doing stateful packet inspection on IPv6, and it sometimes loses an entry in the state table.  The IPv4 firewall code doesn't have this problem and works great.

It's a shame - this would be really great product otherwise, as speeds are great and the modem otherwise seems to do what I'm paying rental fees for it to do (I have static IPs).  I'm kind of frosted about having to pay for a broken modem though, and not having an option to replace it with my own equpipment that works - but I thought I'd see if anyone can help me out or knows of a rental modem that works with IPv6 on Comcast before I complain to the FCC about having to pay rent on a modem with a defect that absolutely impacts user experience (I'll bet Comcast has a ton of "no problem found" closed tickets on DCP3941B's with users reporting "disconnects" or "slow internet" or the like).