Can't import large amount of photos

When I try to import 7 thousand photos, a window says "Unable to import an item This item cannot be added to your photo library because the file is in an unknown format or contains invalid data." with all 7k photos listed appearing. The strange thing about it is that after closing that window and trying to upload one of the photos it says the same, but when I create a new library the same photo successfully uploads there, but if I trying upload the rest, that window appears again and it imports only about 20-30 photos from 7k. But when I reopened the app again with the default library that one photo I was talking about before uploads as well, and if I try to upload other photos everything repeats.