In my efforts to speed up LR, I've been building Smart Previews and then taking the RAW folder (24MP Nikon D750 DNG files) offline via folder rename. Works! But, when I select a set of Smart Previews and try to use Lens Corrections (ENABLE PROFILE CORRECTIONS), LR throws and error "File Not Found". It does work just fine with single image selections. Just not a group.
LR ---does--- apply the lens corrections to the Smart Previews, but when I bring the full-size DNG back online, the lens correction is disabled. That's quite bad behavior!