Massive packet loss to Montreal servers through Level3

Over the last few weeks, I've been running into massive packet loss (16% or more) and latency spikes connecting to servers in a particular Montreal datacenter. I have raised the issue with the service provider, but they advise also contacting the ISP. The IP address in question is 199.91.189.30, but everything in the 199.91.189.0/24 netblock appears to be affected. The problem is worst between 5pm and 11pm UTC-6. Superficially it seems like a problem on their end, given the pathping trace. I don't lose any packets pinging the Comcast DNS servers or Google DNS (8.8.8.8).

Cable modem info:

SMC Networks SMCD3G HW rev 1.01

Network topology:

Static IP with passthrough, DHCP server off, to a Ubiquity EdgeRouter Lite (192.168.1.1) with NAT enabled. IPv4 only.

Signal levels:

Downstream Channel

Traceroute:

Tracing route to 199.91.189.30 over a maximum of 30 hops

1 <1 ms <1 ms <1 ms 192.168.1.1
2 <1 ms <1 ms <1 ms 75-151-200-178-Memphis.hfc.comcastbusiness.net [75.151.200.178]
3 10 ms 11 ms 11 ms 96.120.15.45
4 9 ms 9 ms 8 ms te-0-0-0-3-ur02.dannythomas.tn.malt.comcast.net [68.86.112.165]
5 9 ms 11 ms 11 ms te-0-4-0-2-ar02.winchester.tn.malt.comcast.net [162.151.82.53]
6 19 ms 20 ms 19 ms be-22258-cr02.dallas.tx.ibone.comcast.net [68.86.93.93]
7 * 22 ms 20 ms be-22258-cr02.dallas.tx.ibone.comcast.net [68.86.93.93]
8 * * 69 ms ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
9 56 ms 54 ms 60 ms ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
10 54 ms 53 ms 53 ms ORMUCO-COMM.car2.Montreal2.Level3.net [4.59.178.74]
11 * 53 ms 162 ms 192.34.76.10
12 74 ms 81 ms 71 ms 199.91.189.242
13 75 ms 78 ms 76 ms 199.91.189.30

Pathping trace:

Tracing route to 199.91.189.30 over a maximum of 30 hops

0 technocracy [192.168.1.51]
1 192.168.1.1
2 75-151-200-178-Memphis.hfc.comcastbusiness.net [75.151.200.178]
3 96.120.15.45
4 te-0-0-0-3-ur02.dannythomas.tn.malt.comcast.net [68.86.112.165]
5 te-0-4-0-1-ar02.winchester.tn.malt.comcast.net [162.151.82.49]
6 be-22258-cr02.dallas.tx.ibone.comcast.net [68.86.93.93]
7 be-22258-cr02.dallas.tx.ibone.comcast.net [68.86.93.93]
8 * ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
9 ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
10 ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
11 ORMUCO-COMM.car2.Montreal2.Level3.net [4.59.178.74]
12 192.34.76.10
13 199.91.189.242
14 199.91.189.30

Computing statistics for 350 seconds...
Source to Here This Node/Link
Hop RTT Lost/Sent = Pct Lost/Sent = Pct Address
0 technocracy [192.168.1.51]
0/ 100 = 0% |
1 0ms 0/ 100 = 0% 0/ 100 = 0% 192.168.1.1
0/ 100 = 0% |
2 0ms 0/ 100 = 0% 0/ 100 = 0% 75-151-200-178-Memphis.hfc.comcastbusiness.net [75.151.200.178]
0/ 100 = 0% |
3 8ms 1/ 100 = 1% 1/ 100 = 1% 96.120.15.45
0/ 100 = 0% |
4 10ms 0/ 100 = 0% 0/ 100 = 0% te-0-0-0-3-ur02.dannythomas.tn.malt.comcast.net [68.86.112.165]
0/ 100 = 0% |
5 12ms 0/ 100 = 0% 0/ 100 = 0% te-0-4-0-1-ar02.winchester.tn.malt.comcast.net [162.151.82.49]
0/ 100 = 0% |
6 20ms 0/ 100 = 0% 0/ 100 = 0% be-22258-cr02.dallas.tx.ibone.comcast.net [68.86.93.93]
0/ 100 = 0% |
7 20ms 0/ 100 = 0% 0/ 100 = 0% be-22258-cr02.dallas.tx.ibone.comcast.net [68.86.93.93]
0/ 100 = 0% |
8 81ms 0/ 100 = 0% 0/ 100 = 0% ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
0/ 100 = 0% |
9 81ms 0/ 100 = 0% 0/ 100 = 0% ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
0/ 100 = 0% |
10 84ms 0/ 100 = 0% 0/ 100 = 0% ae-10-10.car2.Montreal2.Level3.net [4.69.153.86]
1/ 100 = 1% |
11 54ms 1/ 100 = 1% 0/ 100 = 0% ORMUCO-COMM.car2.Montreal2.Level3.net [4.59.178.74]
14/ 100 = 14% |
12 75ms 19/ 100 = 19% 4/ 100 = 4% 192.34.76.10
0/ 100 = 0% |
13 74ms 15/ 100 = 15% 0/ 100 = 0% 199.91.189.242
3/ 100 = 3% |
14 73ms 18/ 100 = 18% 0/ 100 = 0% 199.91.189.30

Trace complete.