MB8611 Flaky Signal

I'm a new customer, bought an MB8611 to save on modem rental fees, and also because I'm happy with my existing Google WiFi Mesh network.

Activating service was a problem, so a tech came out and got everything sorted out. Everything seemed to be working for about 48 hours, but I noticed today that my connection seemed unstable. About 60% of the time, I can't get pages to load, even simple Google searches time out, but if I hit refresh enough times, it will eventually load. Running a speed test, I'll get multiple failed page loads, then one will succeed and I'll get 80-90 Mb/s, which is great (I'm on the 100 Mb plan).

I tried rebooting the modem about 50 times, and even factory reset it and reactivated, but no luck. Then I thought it was my Google WiFi router and mesh points but ruled that out by connecting a computer directly to the wired port on the modem - same issues.

After about 3 hours of messing around, I called the xfinity support line and was told I have a great modem, they "sent a signal to it" and everything looked fine from their end. They suggested I contact Motorola so they could patch my modem with an updated configuration. Is that even possible? I went ahead and submitted a support ticket with Motorola's tech support, but I have about zero hope in a resolution there.

Started digging into my modem control panel on 192.168.100.1 and trying to understand what's there, but I can't really tell for sure.

What I know:

1) The blue downstream arrow on the modem is always blinking, which the manual says is a problem and indicates "negotiating multiple downstream bonded channels"

2) My downstream channels look like they might be out of spec, power-wise

3) Earlier, I had over 1.5 million "Corrected" packets on one channel, and 161 thousand on another, but that seems to have dropped to a reasonable level for some reason.

4) Over in the event log, there are a bunch of CM-STATUS code 16, 20, 22, and 24, which have the meanings listed below.

5) I traced my cable line and it looks like it goes straight to a Comcast box on the side of my house, with no line splitters or other junctions in between. The cable is maybe 25 feet long.

CM-STATUS Codes:

16: Downstream OFDM profile failure
FEC errors were over limit on one of the assigned downstream OFDM profiles of a channel

20: NCP profile failure
FEC errors were over limit on NCP

22: NCP profile recovery
FEC recovery on NCP profile

24: OFDM profile recovery
FEC recovery on OFDM profile

Any advice on what I should do? Is Motorola going to save me by pushing some kind of patch to me? Should I return the modem and get a replacement?

Schedule a tech visit to come look at my lines?