Intermittent Connectivity - Comcast support swears no issue

Hi - for several weeks now I have had connectivity issues intermittently. The computer or device will sometimes show they are connected, but won't connect to web pages, email, VPN's, etc. I have called Comcast support several times, and they swear the modem is online and there are no issues, so I think they essentially don't believe me. It has been reset and power cycled multiple times, which will fix the issue temporarily, but it always reoccurs. We have both PC's and Mac's here and it affects them all - sometimes at the same time, and sometimes at different times. It does not seem to affect the MacBook or tablet devices (both Surface and iPad) as much as the Windows based laptops. Please help - this is getting really old....

Modem status downstream:

DCID Freq Power SNR Modulation Octets Correcteds Uncorrectables
Downstream 1 8 655.75 MHz 3.98 dBmV 36.61 dB 256QAM 15269888 2 0
Downstream 2 1 613.75 MHz 3.36 dBmV 36.39 dB 256QAM 13091113 0 0
Downstream 3 2 619.75 MHz 3.08 dBmV 36.17 dB 256QAM 10836868 0 0
Downstream 4 3 625.75 MHz 3.21 dBmV 35.97 dB 256QAM 15159119 1 0
Downstream 5 4 631.75 MHz 3.44 dBmV 36.39 dB 256QAM 15869873 0 0
Downstream 6 5 637.75 MHz 3.80 dBmV 36.84 dB 256QAM 11872438 0 0
Downstream 7 6 643.75 MHz 3.69 dBmV 36.61 dB 256QAM 19560347 0 0
Downstream 8 7 649.75 MHz 3.65 dBmV 36.39 dB 256QAM 13824420 0 0


Upstream:


UCID Freq Power Channel Type Symbol Rate Modulation
Upstream 1 9 36.80 MHz 49.50 dBmV DOCSIS2.0 (ATDMA) 5120 kSym/s 64QAM
Upstream 3 10 30.40 MHz 50.25 dBmV DOCSIS2.0 (ATDMA) 5120 kSym/s 64QAM
Upstream 4 11 25.60 MHz 51.00 dBmV DOCSIS1.x (TDMA) 2560 kSym/s 16QAM