In two of my catalogs, LR refuses to export the GPS and IPTC locations (Sublocation, City, State/Province, Country) of about 3% of the photos having GPS coordinates (117 out of 4300) . LR exports the locations of most of the photos just fine.
This .zip contains a test catalog I exported from one of the catalogs, containing two photos, "good.jpg" and "bad.jpg": https://dl.dropboxusercontent.com/u/21811200/lr-export-bug.2016.04.26.zip
Each photo has a GPS location added by the camera, along with uncommitted location fields added by LR's address suggestions. When the photos are exported as JPEGs with the option Include: All Metadata selected and Remove Location Info unchecked, the location fields are exported to "good.jpg" properly, but not to "bad.jpg". The subfolder "exported-photos" in the .zip contains the exported versions. The originals are in the subfolder "2017".
The problem is not specific to a particular camera -- it occurs with JPEGs from several different cameras and iPhone models and from JPEGs created by LR and by Photoshop Elements.
Tested with LR CC 2015.10 / OS X 10.12.3.