If there was a general problem with DHCP on WiFi connections with LE13 nightlies there'd be a ton of posts on the topic, and there aren't. So whatever the issue is, i'm confident it's local to your environment.
ConnMan debug logs are verbose and somewhat human-readable, but if you have a poor signal the inherent 'noise' that will add to the logs will make it challenging to spot any real issues. Poor signal is not the cause of the invalid-key issue, but as the issue is likely to be an unhandled radio/wireless error condition (the patch on the list is addressing that) poor signal correlates to the problem.