Speed Loss with Gigabit subscription

[staceytheking]

I upgraded to 1gbps speed back in March and updated my cable modem to take advantage of the new plan (new modem is an Arris t25). Ever since then, I get blazing fast speed when the modem first connects (~900mbps), but the speed drops down to ~30mbps after a random period of time. I have been on multiple chats with Xfinity support and the issue keeps occurring. Reboot the modem-->very fast connection-->eventual degradation of speed-->30mbps until I reboot the modem. 

I called Arris support and they told me that the Upstream QAM power was outside of the acceptible range (data posted below) and that this is an Xfinity issue. When I asked about this with Xfinity support, they said that the line looks fine and that it must be an issue with the internal wiring. The cable comes to my house via a buried line that goes from the street to the house, so I hooked up my modem directly to that line (bypassing all internal wiring) and the Upstream QAM power levels did not change (in fact they got lower, which is weird but I'm not an engineer so [insert shrug emoji]). At that point, support said they would re-provision my service and that should fix it. It did not.

This is VERY frustrating. I'm happy to re-wire my house to resolve the issue since Xfinity techs aren't allowed to enter homes, but I'm not convinced that's the answer. Any assistance from these threads would be greatly appreciated.

RF Parameters

Downstream QAM

	DCID	Freq	Power	SNR	Modulation	Octets	Correcteds	Uncorrectables
Downstream 1	1	453.00 MHz	-1.00 dBmV	40.95 dB	256QAM	155451193	0	0
Downstream 2	2	459.00 MHz	-1.30 dBmV	40.37 dB	256QAM	33104877	0	0
Downstream 3	3	465.00 MHz	-1.10 dBmV	40.95 dB	256QAM	33242645	0	0
Downstream 4	4	471.00 MHz	-0.80 dBmV	40.37 dB	256QAM	33257091	0	0
Downstream 5	5	477.00 MHz	-0.50 dBmV	40.95 dB	256QAM	30249213	0	0
Downstream 6	6	483.00 MHz	-0.70 dBmV	40.95 dB	256QAM	32565109	11	0
Downstream 7	7	489.00 MHz	-0.20 dBmV	40.37 dB	256QAM	32402550	0	0
Downstream 8	8	495.00 MHz	-0.10 dBmV	40.37 dB	256QAM	32445804	0	0
Downstream 9	9	507.00 MHz	0.10 dBmV	40.37 dB	256QAM	31056753	10	0
Downstream 10	10	513.00 MHz	0.20 dBmV	40.37 dB	256QAM	33287852	7	0
Downstream 11	11	519.00 MHz	0.00 dBmV	40.37 dB	256QAM	33301379	0	0
Downstream 12	12	525.00 MHz	-0.40 dBmV	40.37 dB	256QAM	33376668	0	0
Downstream 13	13	531.00 MHz	-0.30 dBmV	40.95 dB	256QAM	30953960	0	0
Downstream 14	14	537.00 MHz	-0.10 dBmV	40.37 dB	256QAM	33253055	0	0
Downstream 15	15	543.00 MHz	-0.30 dBmV	40.95 dB	256QAM	33290730	0	0
Downstream 16	16	549.00 MHz	-0.70 dBmV	40.95 dB	256QAM	33367718	0	0
Downstream 17	17	555.00 MHz	-0.30 dBmV	40.95 dB	256QAM	31005923	0	0
Downstream 18	18	561.00 MHz	0.00 dBmV	40.37 dB	256QAM	33411325	0	0
Downstream 19	19	567.00 MHz	-0.30 dBmV	40.37 dB	256QAM	33331893	0	0
Downstream 20	20	573.00 MHz	-0.40 dBmV	40.37 dB	256QAM	33211846	0	0
Downstream 21	21	579.00 MHz	0.20 dBmV	40.95 dB	256QAM	30977485	0	0
Downstream 22	22	585.00 MHz	-0.20 dBmV	40.37 dB	256QAM	33330472	0	0
Downstream 23	23	591.00 MHz	-0.40 dBmV	40.37 dB	256QAM	33433711	0	0
Downstream 24	24	597.00 MHz	-0.30 dBmV	40.37 dB	256QAM	33267164	0	0
Downstream 25	25	603.00 MHz	-0.30 dBmV	40.95 dB	256QAM	32868246	0	0
Downstream 26	26	609.00 MHz	-0.30 dBmV	40.37 dB	256QAM	35508942	0	0
Downstream 27	27	615.00 MHz	-0.30 dBmV	40.95 dB	256QAM	35539254	0	0
Downstream 28	28	621.00 MHz	-0.40 dBmV	40.37 dB	256QAM	35531400	0	0
Downstream 29	29	627.00 MHz	0.20 dBmV	40.95 dB	256QAM	32869722	0	0
Downstream 30	30	633.00 MHz	0.00 dBmV	40.37 dB	256QAM	35560321	0	0
Downstream 31	31	639.00 MHz	-0.50 dBmV	40.37 dB	256QAM	35450554	0	0
Downstream 32	32	645.00 MHz	-0.20 dBmV	40.37 dB	256QAM	35548701	0	0

Reset FEC Counters

Downstream OFDM

	FFT Type	Channel Width(MHz)	# of Active Subcarriers	First Active Subcarrier(MHz)	Last Active Subcarrier(MHz)	Average RxMER(dB)
						Pilot	PLC	Data
Downstream 2	4K	50	1004	697	748	49	42	43

Upstream QAM

	UCID	Freq	Power	Channel Type	Symbol Rate	Modulation
Upstream 1	3	23.70 MHz	38.25 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM
Upstream 2	4	17.30 MHz	38.25 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM
Upstream 3	2	30.10 MHz	38.75 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM
Upstream 4	1	36.50 MHz	38.75 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM