CM1150 modem vs. Comcast vs. Roku

I'm using a CM1150 modem with voice for my Comcast service. Internet connection typically last for about 1/2 a day before it degrades and we have to restart the modem.  it has been online for 14 months.  It would do this problem for about a week and then it was good for a month or two before going through the cycle again.  Recently it is non stop.  I have set the moden back to factory defaults which was good for 2 (maybe) days. 

I use a TP LINK router for wifi - rebooting it doesn't seem to help

1st clue that things are going bad is the Roku streaming stick craps out - then my son's computer wifi connection finally crashes.  most of the time the downstream LED is blinking, sometimes the upstream is blinking instead

Comcast service comes from the pole on the street - into the house - to a splitter - one way to the tv/dvr - other way to the modem.  I notice there is a filter for Comcast DVR on the supply side of the splitter (should that be on the other side of the splitter/DVR side?)

Netgear interfaces shows that 1-31 downstream channels are normally locked  (32 is not) and 1-4 Upstream channels are locked

I would prefer to solve the problem than to trust Comcast that it's the modem's fault and buy as new modem

included are some screen shots of the netgear pages