Used to have the same issue with lenses of unknown focal length. LR assigns default values to certain fields in the EXIF data when they are blank. On the import tab there were options, LR5, to change these default behaviours. Would expect the CC version to be the same in that regard unless it is something else that Adobe decided to take away at some point.
You also mentioned that there was a recent update. Occasionally updates would change default behaviours and reset which profile to apply at import to the original default profile rather than my custom ones.