lightroom- Unable to save jpgs to usb drive

I am unable to upload certain files even though I can preview them from the SD card. Then if I do upload the CR2 files and JPG’s and do the editing, randomly some can’t be simply saved onto a 3.0 usb drive. Can anyone please help me with this, it is my friends wedding photos and I don’t not want to leave any photos out due to a uploading/exporting error.

At this time only 953 photos of 3,042 have been successfully converted and saved onto the usb drive.