Trying to relocate 2467 files but only 1185 of them are actually relocated

In a directory, I have 2467 Nikon RAW files. They were offline and I wanted to relocate them. So I selected the directory and clicked on Locate. At first Capture One crashed and I had to reload the programme. Then I did it again et it worked... except that it relocated only the first 1185 files.

The directory isn't marked as offline any more in Capture One but the 1282 un-relocated files are now invisible.  Yet there is no technical difference between the relocated files and the skipped ones: they are all NEF files, they are in the same size range, and they share the same name structure (from xxx_0001 to xxx_2467). Even the time stamps can't explain the problem: the first overlooked image was taken a fraction of a second after the last relocated one.

Does anyone know what happened and what I must do? Thank you very much in advance for your help.