intermittent packet loss, questions regarding modem signal values

hey. id like to open with the statement that ive read the sticky, and im aware of the increased traffic. im looking for any input on performed testing and received values before i call ISP and assure them it aint on me.

equipment:

netgear gateway c6300BD [2.4ghz/5ghz radios disabled, only lan port used is to WAN port of router, effectively performing as simply a modem]

netgear router r6400 [behaving as router, not wireless ap]

3 wired connections to router, 2 of those spend about 95% of day idle. two cable boxes connected directly to coax outlets, no splitters in use.

so far ive:

- replaced all coax

- replaced all ethernet

- replaced modem with official cox gateway i had on hand that was only used for 2 months

- moved gateway between all available coax connections

- connected primary pc directly to gateway / turned router into access point and used gateway for everything

- moved all networking components to dedicated outlets / diff power supplies

- applied QoS rules thru router to prioritize packet delivery for game of choice

where im at right now:

basically, the coax cable directly from service box provides best signal to modem. it is fed directly into room from box, not thru an outlet. no splitters on this connection (or in the house at all) (sidenote: this is the one coax connection i could not personally replace being in the service box, but the cable seems fine to me)

when i first boot my gateway/modem (from now on im going to refer to this as my modem, the r6400 handles all traffic routing) these are the values i see:

the upstream values are on the low end, but still within 'operable' range. but *** look at those sweet **** downstream values. i like that.

well of course until i do anything bandwidth intensive, like a speedtest in this case

this is always met with the same three events from my modem, in some combination:

2020-12-21, 11:56:27.0	Warning (5)	Unicast DSID PSN startup error
2020-12-21, 11:45:00.0	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2020-12-21, 11:44:12.0	Notice (6)	TLV-11 - unrecognized OID;

(identifying info removed)

the tlv-11 one ive only seen once since ive cleared logs (got a little overconfident thinking i made progress) but this morning i havent experienced any t3 timeouts, but theyre always there too

also, a speed test is not required for this to occur, it will occur on its own over time, especially with high bandwidth usage. this is just a way to reproduce on command.

so, like why? why is this happening? this specific repeatable occurrence always ends in network jitter of some sort, up to and including lost packets. if the downstream channels are locked, why is it jumping ship? my upstream is the questionable stuff. 

do i need to contact cox to have my modem reprovisioned to accept this frequency range or something?

would an upstream amplifier help? (i doubt it would help this specific issue but really my upstream **, and that ** for games/voip, i work from home)

ive done everything in my knowledge and learned a bunch more to troubleshoot this and im out of ideas. i understand the network congestion rn but im out of people to blame but cox at this point. please let me know if theres a huge gap in my understanding of the situation (very possible)

oh and heres a ping i had running ever since i rebooted the modem and router and started writing this post [roughly 20mins]

ping google.com -4 -t

Ping statistics for 172.217.5.78:
Packets: Sent = 1477, Received = 1475, Lost = 2 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 11ms, Maximum = 132ms, Average = 17ms

average paints a better picture than reality

i mean like im a realist, i know the internet aint some perfect machine. but this type of performance over 20 minutes of slow **** windows pings (dont get me started on 128packet/sec transmission) is pretty laughable dude. someone help me to realize something stupid ive completely missed please

thanks for reading