Intermittent drops several times a day; ingress on 471–507 MHz downstream channels (Hitron CODA56)

For about the past week the internet has dropped several times a day, each time for 30–90 seconds. I use my own modem, a Hitron CODA56 on firmware 7.3.5.3.2b1, connected to a UniFi gateway that logs every drop and fails over to a cellular backup. I’ve ruled out my own equipment and the modem’s signal points to a line problem, so I’m asking for a technician to check the drop for ingress.

Drops logged by the gateway (ET):

• Oct 25: ~5:16 PM, 6:29 PM, 7:14 PM
• Oct 26: 4:31 PM, 6:52 PM
• Oct 29: 9:28 AM, 6:41 PM
• Oct 30: 1:58 PM, 3:59 PM

Most drops are preceded by packet loss or high latency for about a minute. During the Oct 30 1:58 PM event, latency to 75.75.75.75 hit 7.5 seconds.

Ruled out on my side:

• The modem isn’t rebooting. Uptime is 521 hours (about 21 days) and spans every drop.
• The Ethernet link between modem and gateway is clean. It holds 2.5G full duplex with zero CRC or frame errors, and the gateway’s interface counters show the link stayed up through the drops.
• During a drop, the gateway can still reach the modem. Traffic stops past the modem: it loses packets to Comcast’s own DNS (75.75.75.75).

Downstream signal. Power is normal on all channels (−1 to +5 dBmV). Three channels have low SNR and very large uncorrectable counts:

The other 29 SC-QAM channels are at 37–40 dB with essentially zero uncorrectables. The OFDM channel is at 41 dB.

Upstream: 5 ATDMA channels at 45.5–47.0 dBmV.

Errors concentrated in a narrow band like this, with normal power everywhere else, look like ingress in the line. The drop to the house is a long underground run (about 1,000 ft) through wet ground.

The coax inside the house has been checked: no unneeded splitters, and connectors are tight and corrosion-free from the entry point to the modem.

Could someone check my line’s SNR and T3/T4 history from your side and schedule a technician to check the drop and tap for ingress? I can send account details by DM.