2015-08-16 13:59:17 translatewiki.net translatewiki_net-bw_: [c2d6f10c] /w/api.php MWException from line 886 of /srv/mediawiki/tags/2015-08-15_20:04:03/includes/changes/RecentChange.php: Attempt to write "2a02:810d:1440:" as an IP address into recent changes
So MW doesn't think that IPv6 address is valid, which is correct https://github.com/wikimedia/mediawiki/blob/master/includes/changes/RecentChange.php#L884-L887
The question here really is why an invalid IP address is getting that far; what's giving that address? Or is it already saved in the DB prior to some validation that now exists?
It is a probably part of an an address of admin user using Special:ManageTranslatorSandbox page calling ApiTranslateSandbox. No idea why we would get truncated IP address in one of the log events created by that API.