Extremely slow download suddenly (350k), yet upload remains fine at near 700k.

[#1]

EDIT: After 4 hours of struggling, it suddenly sprung back to life. See next post...
ROUTER: TG58N with 10.2.2.B firmware.
Connection before reset (see later): DSL Type: ITU-T G.992.5 Bandwidth (Up/Down) [kbps/kbps]: 888 / 4,290  Uptime: 3 days, 14:25:30
Broadband is virtually unusable this morning. So I did a speedtest:
358kb down, 652kb up

I did a "normal" reboot of the modem, and found myself locked out. So then I did a "full factory reset hard reboot" (hold reset until lights go out), and could get back in with the default password on the card.
Oddly, it had remembered my username and connected itself OK.
I managed to get in a couple of pages, then it started saying:

Access Error: 500 -- Internal Server Error

I was able to get to the terminal, but not really sure what I'm doing there!
Still got 4Mb/800k connection, but still getting VERY slow down, normal up.
I checked my SamKnows whitebox report card - speed fell dramatically on about the 10th of October - see attachment.
Also, this doesn't seem to be a normal pattern of packet loss during the night when nothing is connected (phones off, chromecast off etc)  ... or does it?
Finally the last two attachments show the results of the BT Wholesale Speedtest, including the third "disconnect and change username" test.... not looking good!
I've checked outages and exchange reports in my area. Nothing showing up as wrong.
BTW, I have logged a ticket, but these things can take a while, so I'm posting here in case anyone has any ideas!
In case any of the below rings alarm bells, here's the router stats before I rebooted it:

Uptime:	3 days, 14:25:30
DSL Type:	ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]:	888 / 4,290
Data Transferred (Sent/Received) [GB/GB]:	1.11 / 7.44
Output Power (Up/Down) [dBm]:	12.8 / 0.0
Line Attenuation (Up/Down) [dB]:	26.3 / 49.5
SN Margin (Up/Down) [dB]:	6.6 / 10.3
System Vendor ID (Local/Remote):	TMMB / ----
Chipset Vendor ID (Local/Remote):	BDCM / IFTN
Loss of Framing (Local/Remote):	0 / 0
Loss of Signal (Local/Remote):	0 / 0
Loss of Power (Local/Remote):	0 / 0
Loss of Link (Remote):	-
Error Seconds (Local/Remote):	80 / 0
FEC Errors (Up/Down):	9,340 / 432,237
CRC Errors (Up/Down):	70 / 115
HEC Errors (Up/Down):	136 / 605

Oh, and here's a tracert to the beeb - even the local router seems slightly longer pings than normal, but it's the second "hop" that really seems to grind....

Tracing route to newswww.bbc.net.uk [212.58.244.132]
over a maximum of 30 hops:
 1   261 ms   170 ms   306 ms  192.168.1.254
  2  2668 ms   304 ms   297 ms  lo0-central10.ptw-ag04.plus.net [195.166.128.194]
  3     *       71 ms   108 ms  link-b-central10.ptw-gw02.plus.net [212.159.2.158]
  4   389 ms   718 ms   449 ms  xe-7-2-0.ptw-cr02.plus.net [212.159.0.254]
  5    44 ms    37 ms    49 ms  ae2.ptw-cr01.plus.net [195.166.129.4]
  6    75 ms   118 ms    41 ms  kingston-gw.thdo.bbc.co.uk [212.58.239.6]
  7     *        *        *     Request timed out.
  8     *        *        *     Request timed out.
  9    83 ms    87 ms   240 ms  ae0.er01.telhc.bbc.co.uk [132.185.254.109]
 10   360 ms   319 ms   119 ms  132.185.255.149
 11   144 ms   128 ms    47 ms  212.58.244.132

BTW, I've unplugged all other items, disconnected the whitebox, plugged the router into the test socket and am connected directly to the router via LAN cable, which makes that first "hop" ping time seem very long, and in conjunction with the internal server errors, I wonder if the router if flaking? Doesn't explain the fast up/slow down thing though... hmmmm

[#2]

UPDATE: After spending four hours of frustration gathering info, mucking about etc, it's suddenly sprung back to life again - well, OK, still slower than 90% of the rest of the UK, but "normal" for us.
Note that the upload speed is the same though...

Hmmm... I wonder what caused that?

[#3]

Hi Racquel
Sorry to hear of the problems that you have experienced in regards to your speeds, but I'm glad to hear that this has been restored to speeds that you would expect from your line.
I will aim to monitor the connection over the next few days to ensure that what occurred was only an anomaly, but if you find that the problem reoccurs then please don't hesitate to get back in touch
Regards
Matt

[#4]

Quote from: Cruise85

I will aim to monitor the connection over the next few days to ensure that what occurred was only an anomaly, but if you find that the problem reoccurs then please don't hesitate to get back in touch

Still seems to be OK, although I've totally dropped my IPV6 tunnel via sixxs as I can't seem to reach Google services; not sure if that's you or sixxs.
Anyway, any idea how backlogged support are right now? Last action on the ticket is:

Quote

"11:16am, Wednesday 15 Oct 2014 We are currently performing tests on your broadband service which will allow us to investigate the problem you've reported. Please be aware if this is a new fault that this can take up to 24 hours. We'll contact you as soon as we have more information and let you know what happens next."

[#5]

Hi racquel
Glad to hear that the speeds have remained usable and they haven't dropped again
In regards to the fault ticket, fault are currently getting picked up in a time scale of around 72 hours, but I'll give on of the faults team a nudge today and ask them to look into it for you
Regards
Matt

[#6]

Quote from: Cruise85

In regards to the fault ticket, fault are currently getting picked up in a time scale of around 72 hours, but I'll give on of the faults team a nudge today and ask them to look into it for you

Wow - glad mine came back to life on its own! 3 days is quite a long time to even get round to picking up the ticket.
No urgency, I was just interested to know what had happened, and why. Thanks!