Error Exporting Photos from Photos

Hello, I'm trying to get all of my photos moved off my laptop and onto an external hard drive -- in doing this, I want to export them out of Photos so I don't have to go through the app forever. I have around 25,000 images to move. Every time I try to move them, it tells me there is an error and it is unable to complete ANY of the copies. I've tried exporting them onto two different external hard drives, onto my desktop, and I've also tried selecting smaller sections of only 200 photos. Nothing works. HELP! I need those photos off my computer because I'm constantly getting hit with "scratch disc is full" errors when I'm working, and I'm so frustrated I can't get these images out of Photos.