Arris S34 drops and signal loss

I've had an Arris S34 for about a year on a 1 Gig plan in Denver. Recently there have been increasing connection drops. Short ones stutter the TV stream, and a couple per week take the whole connection down, including an upload outage last week where Ookla showed 288 Mbps down and 0 up. Normal tests since then land around 400–600 down and 20-30 up, nowhere near the plan.

I had a tech out on October 1. The line tested good on his meter: about 2500 down and 87–98 up at the modem, lost syncs 0 during the visit. The boot file on his handheld was d11_m_s34_subnxmgig_c01.cm. 

My modem log repeatedly shows Critical and Warning errors. On a reprovision that morning the CMTS offered the 85 MHz upstream diplexer and the S34 ignored it, then came back on 5–42 MHz. Right after that it logged the DRW warning, commanded power more than 6 dB below the top of the window. Before and since the visit the event log repeated Loss of Sync and T3 timeouts every few minutes.

[Edited: "Personal Information”] 

From other S34 threads it looks like the fix is the special code that forces the next-gen config, which I was hoping would fix my issues as it's getting difficulty to work from home or enjoy streaming services.