I'm sorry to reply to such an old topic, we've had this issue in the past at a site, but we just got a customer who has new Optimum (formerly suddenlink) coax service in Texas and I'm seeing this issue. The optimum tech I talked to is definitely aware of something. He asked about my firmware version (18.107.10 on an MX100) The MX arps for the gateway and gets no response. If @Nash ever became aware of a fix or anyone else who might read it, would love to hear. My Optimum ticket has been escalated to engineering.
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