What version of LR 6 are you using? There is a specific bug with LR 6.5 (and CC 2015.5) where LR doesn’t handle lens types properly for some cameras.
You can revert to LR 6.4 (or CC 2015.4) by uninstalling LR completely, then downloading and installing the xxx.0 installer, then download and install the xxx.4 installer from here:
Version 6.5 the monthly one for $9.99. Will the bug be fixed at some point?
This is a known issue and Adobe should be releasing an x.5.1 version of LR soon to address a few things like this. I don't know when, exactly, but much sooner than the normal x.6 version that would take several months.