A significant bug in version 6.5 caused EXIF lens names to be stripped for certain Nikon cameras during import. Version 6.5.1 automatically resolved this, allowing lens data to populate correctly again.
Adobe Photoshop Lightroom 6.5.1 (also released as Lightroom CC 2015.5.1) was a maintenance update released on April 28, 2016 adobe photoshop lightroom cc 6.5.1
for a full feature summary of the 2015/Lightroom 6 lifecycle. Photography Bay A significant bug in version 6
The 6.5.1 update addressed several critical issues found in the previous 6.5 version: EXIF Metadata Restoration: adobe photoshop lightroom cc 6.5.1