CM1000v2 modem with slow speeds of 480mbps

Your cable connection logs show a couple of things.

First, your signal power levels are good.  The modem expects signal power levels between +7 and -7 dBmV.  Yours are basically in the middle.  The dynamic range is very good. Info for reference: https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router.

Your correctable/uncorrectable code words show some significant values.  These are transmission errors and should essentially be zero.  On the connection page, these values accumulate over time since the modem was last booted.  Your screen snips did not show the system up time so I do not know if these values accumulated over a few hours, a few days, a few weeks or ?.

Recommend your pull the power cord on your modem, restart it and monitor the code word values.  Right after the restart, they should all be zero.  The page does not update in real time.  When you access the page, the values are a snapshot in time.  To get new values, you have to go to a different page and then come back.

Continued correctable/uncorrectable signal errors are the responsibility of the ISP.  Xfinity has been doing significant upgrade work in my area and there are time frames with a lot of transmission errors and a lot of disconnects.

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Alpha1991 wrote:
Here is the thing when I ran a test on DUMA OS
Now I have 921/212.0 mbps
41/23 MBps
Max Ping 12.98

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When compared to your throughput on June 13, these numbers are a direct indication you have just been through the Xfinity mid-split upgrade.  That is why you are showing the 200+ Mbps upload and why your download has been sporadic in the previous few weeks.  It may take a few weeks for Xfinity to fine tune their new hardware.  Then your service should settle down.  What area of the country do you live in?

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Alpha1991 wrote:
In New Jersey, but I am surprise they never said anything or send out a later they are doing upgrades. Since it effected my system. Isn’t the reason why some of us pay so muck for internet?

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Some Xfinity regions do a better job than others of notifying customers of changes.   Notifications in the Seattle area are seldom made.

The Nighthawk mobile application keeps a good history record of your throughput tests.  Recommend you monitor the results for a couple of weeks to determine if it maintains your performance.