Accounting server cannot be reached since 2016-01-27

For a few years I've been running my TS3 server without problems. Since about 2 weeks, my server shuts down every 2 hours because it claims it cannot reach accounting.teamspeak.com:

Code:

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2016-02-11 10:26:58.877409|INFO    |ServerLibPriv |  |TeamSpeak 3 Server 3.0.12.1 (2016-02-08 15:34:38)
2016-02-11 10:26:58.877843|INFO    |ServerLibPriv |  |SystemInformation: Linux 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt20-1+deb8u3 (2016-01-17) x86_64 Binary: 64bit
2016-02-11 10:26:58.877879|WARNING |ServerLibPriv |  |The system locale is set to "C" this can cause unexpected behavior. We advice you to repair your locale!
2016-02-11 10:26:58.878731|INFO    |DatabaseQuery |  |dbPlugin name:    SQLite3 plugin, Version 2, (c)TeamSpeak Systems GmbH
2016-02-11 10:26:58.878769|INFO    |DatabaseQuery |  |dbPlugin version: 3.8.6
2016-02-11 10:26:58.879000|INFO    |DatabaseQuery |  |checking database integrity (may take a while)
2016-02-11 10:26:59.060294|INFO    |Accounting    |  |Licensing Information
2016-02-11 10:26:59.060379|INFO    |Accounting    |  |type              : Non-profit
2016-02-11 10:26:59.060421|INFO    |Accounting    |  |starting date    : Mon Aug 31 00:00:00 2015
2016-02-11 10:26:59.060446|INFO    |Accounting    |  |ending date      : Fri Mar 11 00:00:00 2016
2016-02-11 10:26:59.060467|INFO    |Accounting    |  |max virtualservers: 10
2016-02-11 10:26:59.060488|INFO    |Accounting    |  |max slots        : 512
2016-02-11 10:27:00.115726|INFO    |              |  |Puzzle precompute time: 1048
2016-02-11 10:27:00.116188|INFO    |FileManager  |  |listening on 0.0.0.0:30033
2016-02-11 10:27:00.123960|WARNING |              |  |loadFromDatabase() found unregistered ident: virtualserver_antiflood_points_needed_command_stop
2016-02-11 10:27:00.124021|WARNING |              |  |loadFromDatabase() found unregistered ident: virtualserver_antiflood_points_needed_ip_ban
2016-02-11 10:27:00.316911|WARNING |              |  |loadFromDatabase() found unregistered ident: virtualserver_antiflood_points_needed_command_stop
2016-02-11 10:27:00.316945|WARNING |              |  |loadFromDatabase() found unregistered ident: virtualserver_antiflood_points_needed_ip_ban
2016-02-11 10:27:00.396940|INFO    |CIDRManager  |  |updated query_ip_whitelist ips: 127.0.0.1,
2016-02-11 10:27:00.397630|INFO    |Query        |  |listening on 0.0.0.0:10011
2016-02-11 10:28:00.482409|WARNING |              |  |Accounting connection stalled
2016-02-11 10:29:20.010142|ERROR  |              |  |read invalid packet size size
2016-02-11 11:30:21.305729|WARNING |              |  |Accounting connection stalled
2016-02-11 11:31:40.018014|ERROR  |              |  |read invalid packet size size
2016-02-11 12:32:42.638430|WARNING |              |  |Accounting connection stalled
2016-02-11 12:34:00.065408|ERROR  |              |  |read invalid packet size size
2016-02-11 12:34:00.065520|ERROR  |Accounting    |  |Could not connect to accounting server after multiple attempts, shutting down server

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I have no rules blocking outgoing traffic in the firewall and I appear to be able to connect to accounting.teamspeak.com just fine:

Code:

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teamspeak:~$ nc -v accounting.teamspeak.com 2008
Warning: inverse host lookup failed for 128.65.210.118: Unknown host
accounting.teamspeak.com [128.65.210.118] 2008 (?) open

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Anything else I could check?

Accounting server cannot be reached since 2016-01-27