I have been having problem with my upstream for a couple of weeks. I even went as far as purchasing a new SB6141 modem which appeared to have corrected the issue for a while.
My upstream bonding drops from 3 channels to just one and the power level goes through the roof. (From 51dBmV to 57dBmV)
This is usually accompanied by T4 timeouts and a modem reboot (Screen shots attached)
Check all of the coax connections for tightness and corrosion, and replace any older crimp style connectors with compression connectors. Also connect your modem directly to your demarc (the first connection in your home before any splitters); that will eliminate inside wiring and splitters as the source of the problem. If that doesn't help, then you will need to ask Comcast support for help. -- A well-regulated militia, being necessary to the security of a free State, the right of the people to keep and bear arms shall not be infringed.
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