With the update to LR 2015.10, not all of my previously LR imported videos are recognized as already imported by LR. With subsequent Imports, random video files are showing as "new" when they should be dimmed out.
I have compared the source file names, file size and date stamps to the files residing on my drive from the previous import and there are no differences. The previous import was performed with version 2015.10. The video files that are not recognized are random - some video files taken same day with same camera imported in the same batch are recognized as imported. Length of video doesn't seem to be a factor.
I am using Copy, but selecting Copy as DNG, Move or Add makes no difference. Don't Import Suspected Duplicates is checked but turning off has no effect.