In the specific case of amazonaws.com the issue may be connected to adblock.
# /etc/init.d/adblock query amazonaws.com
::: results for domain 'amazonaws.com'
+ amazonaws.com
After whitelisting, resolving works again. For now at least.
I am confused by the fact, that it has worked for some time, then not.
Also I am still wondering how to gather the logs. The debugger stops for some reason or logging is restarted so there is nothing useful in the log anymore.
Just spotted:
2018-11-02 13:12:01 notice syslog-ng[17834]: syslog-ng shutting down; version='3.10.1'