bitcoin: trying to sync new testnet node - failing due to "stalling block download"

I’ve been trying to sync testnet for a few weeks now. It keeps getting stuck. The logs are full of messages about “stalling block download”.

Here’s an example:

2017-08-12 21:59:29 Loaded 31249 addresses from peers.dat  144ms
2017-08-12 21:59:29 init message: Loading banlist...
2017-08-12 21:59:30 init message: Starting network threads...
2017-08-12 21:59:30 net thread start
2017-08-12 21:59:30 dnsseed thread start
2017-08-12 21:59:30 addcon thread start
2017-08-12 21:59:30 init message: Done loading
2017-08-12 21:59:30 msghand thread start
2017-08-12 21:59:30 opencon thread start
2017-08-12 21:59:30 GUI: Platform customization: "other"
2017-08-12 21:59:30 GUI: PaymentServer::LoadRootCAs: Loaded  170  root certificates
2017-08-12 21:59:30 receive version message: /Satoshi:0.13.2/: version 70015, blocks=1176613, us=<my-ip>:32239, peer=0
2017-08-12 21:59:31 receive version message: /Satoshi:0.13.2/: version 70015, blocks=1176613, us=<my-ip>:15189, peer=1
2017-08-12 21:59:32 ProcessMessages(version, 102 bytes) FAILED peer=2
2017-08-12 21:59:32 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:16892, peer=3
2017-08-12 21:59:33 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:29573, peer=4
2017-08-12 21:59:33 Peer=0 is stalling block download, disconnecting
2017-08-12 21:59:34 receive version message: /Satoshi:0.14.0/: version 70015, blocks=1176613, us=<my-ip>:29163, peer=5
2017-08-12 21:59:34 connect() to [2602:306:3718:2560:31c5:6402:4150:fe74]:18333 failed: Network is unreachable (101)
2017-08-12 21:59:35 connect() to [2001:0:9d38:6abd:3c72:2f62:f5ff:fffb]:18333 failed: Network is unreachable (101)
2017-08-12 21:59:35 Peer=1 is stalling block download, disconnecting
2017-08-12 21:59:35 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:13541, peer=6
2017-08-12 21:59:36 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:31431, peer=7
2017-08-12 21:59:37 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:16946, peer=8
2017-08-12 21:59:37 receive version message: /Satoshi:0.14.1(UASF-SegWit-BIP148)/: version 70015, blocks=1176613, us=<my-ip>:1524, peer=9
2017-08-12 21:59:38 Peer=3 is stalling block download, disconnecting
2017-08-12 21:59:40 Peer=4 is stalling block download, disconnecting
2017-08-12 21:59:41 P2P peers available. Skipped DNS seeding.
2017-08-12 21:59:41 dnsseed thread exit
2017-08-12 21:59:42 Peer=5 is stalling block download, disconnecting
2017-08-12 21:59:44 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:19638, peer=10
2017-08-12 21:59:44 Peer=6 is stalling block download, disconnecting
2017-08-12 21:59:46 Peer=7 is stalling block download, disconnecting
2017-08-12 21:59:48 Peer=8 is stalling block download, disconnecting
2017-08-12 21:59:50 receive version message: /Satoshi:0.14.1/: version 70015, blocks=1176613, us=<my-ip>:31236, peer=11
2017-08-12 21:59:50 Peer=9 is stalling block download, disconnecting
2017-08-12 21:59:52 Peer=10 is stalling block download, disconnecting
2017-08-12 21:59:56 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:1951, peer=12
2017-08-12 21:59:57 receive version message: /Satoshi:0.13.2/: version 70015, blocks=1176613, us=<my-ip>:17679, peer=13
2017-08-12 21:59:57 receive version message: /Satoshi:0.14.0/: version 70015, blocks=1176613, us=<my-ip>:12698, peer=14
2017-08-12 21:59:58 connect() to [2001:0:9d38:6ab8:2c22:7efc:46f0:c0b2]:18333 failed: Network is unreachable (101)
2017-08-12 21:59:59 Peer=11 is stalling block download, disconnecting
2017-08-12 21:59:59 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:14820, peer=15
2017-08-12 21:59:59 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176613, us=<my-ip>:22808, peer=16
2017-08-12 22:00:00 receive version message: /Satoshi:0.13.0/: version 70014, blocks=1176614, us=<my-ip>:18306, peer=17
2017-08-12 22:00:01 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176614, us=<my-ip>:13932, peer=18
2017-08-12 22:00:01 Peer=12 is stalling block download, disconnecting
2017-08-12 22:00:01 connect() to [2001:0:5ef5:79fd:2826:209:d9b2:d42f]:18333 failed: Network is unreachable (101)
2017-08-12 22:00:03 Peer=13 is stalling block download, disconnecting
2017-08-12 22:00:05 Peer=14 is stalling block download, disconnecting
2017-08-12 22:00:07 connect() to [2001:0:9d38:90d7:3060:a2:ace1:d935]:18333 failed: Network is unreachable (101)
2017-08-12 22:00:07 Peer=15 is stalling block download, disconnecting
2017-08-12 22:00:08 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176614, us=<my-ip>:6427, peer=19
2017-08-12 22:00:09 receive version message: /Satoshi:0.14.0/: version 70015, blocks=1176614, us=<my-ip>:4919, peer=20
2017-08-12 22:00:09 receive version message: /Satoshi:0.13.0/: version 70014, blocks=1096309, us=<my-ip>:15127, peer=21
2017-08-12 22:00:09 Peer=16 is stalling block download, disconnecting
2017-08-12 22:00:10 receive version message: /Satoshi:0.14.1/: version 70015, blocks=1176614, us=<my-ip>:28165, peer=22
2017-08-12 22:00:11 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176614, us=<my-ip>:17486, peer=23
2017-08-12 22:00:11 receive version message: /Satoshi:0.13.2/: version 70015, blocks=1176614, us=<my-ip>:25716, peer=24
2017-08-12 22:00:12 Peer=17 is stalling block download, disconnecting
2017-08-12 22:00:12 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176614, us=<my-ip>:22900, peer=25
2017-08-12 22:00:14 Peer=18 is stalling block download, disconnecting
2017-08-12 22:00:16 Peer=19 is stalling block download, disconnecting
2017-08-12 22:00:18 Peer=20 is stalling block download, disconnecting

I built from source on Linux, against tag v0.14.2.

Three minutes later I’ve still not made any progress:

2017-08-12 22:02:56 Peer=74 is stalling block download, disconnecting
2017-08-12 22:02:57 receive version message: /Satoshi:0.13.99/: version 70015, blocks=1176617, us=<my-ip>:18117, peer=77
2017-08-12 22:02:59 Peer=75 is stalling block download, disconnecting
2017-08-12 22:03:01 Peer=76 is stalling block download, disconnecting
2017-08-12 22:03:03 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176617, us=<my-ip>:22069, peer=78
2017-08-12 22:03:04 receive version message: /bcoin:v1.0.0-beta.12/: version 70015, blocks=1166749, us=<my-ip>:26790, peer=79
2017-08-12 22:03:05 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176617, us=<my-ip>:29893, peer=80
2017-08-12 22:03:05 Peer=77 is stalling block download, disconnecting
2017-08-12 22:03:05 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176617, us=<my-ip>:13425, peer=81
2017-08-12 22:03:06 connect() to [2003:78:ef5f:4c00:55ab:d1f0:9b1d:ca53]:18333 failed: Network is unreachable (101)
2017-08-12 22:03:07 Peer=78 is stalling block download, disconnecting
2017-08-12 22:03:07 receive version message: /Satoshi:0.14.2/: version 70015, blocks=1176617, us=<my-ip>:29658, peer=82
2017-08-12 22:03:09 Peer=80 is stalling block download, disconnecting
2017-08-12 22:03:12 Peer=81 is stalling block download, disconnecting
2017-08-12 22:03:14 Peer=79 is stalling block download, disconnecting

Is this a problem with testnet? With having segregated witness activated? With my Internet being a bit laggy?