WAN disconnect only during high speed (>8mb/s) download - Time Warner Internet

This question is about "WAN disconnect only during high speed (>8mb/s) download", with Time Warner Cable internet and apps. Hi - wondering if anyone can help me troubleshoot an issue i'm having with my network.

I have a TG1672G with TWC 300mbps service.

It is bridged to my home LAN - multiple speed tests across the LAN from point to point show a consistent 650-800mpbs throughput and sustained local large file transfers have no issues.

The reason i mention that is because during high-speed WAN downloads - from say Dropbox or Google Drive, or any site that can sustain a download in the higher ranges, if the browser download speed gets above 8mb/s or so for a file of over several hundred MB, at some point the WAN connection will be lost. The modem will of course reconnect but it means the download has to be restarted.

The curious thing to me is that if is, for example, a 1gb file download at 3MB/s - no issue at all. Whereas another 1gb download that can reach over 8mb/s - almost certain to have an interupt.

Obviously to effectively troubleshoot i would like to provide useful details - the event log on the Arris has no entry for any of the events. The Cisco router (RV320) simply shows a 'WAN connection down' message followed 30s later by a 'WAN connection is up' message.

Can anyone suggest a suitable approach to effectively troubleshoot the issue? And any more details that would be helpful.

I suppose a good overall question is "What scenarios would only cause high data-rate downloads to fail?"

Many thanks

This topic covered WAN disconnect only during high speed (>8mb/s) download, and TWC cable internet service.