Sudden Import error - 9937 when using image capture

Hi, I'm suddenly getting an error message when I'm trying to import pics and videos from my Iphone using image capture. This started very suddenly, while I was in the middle of importing a bunch of pics and videos. I'm importing them to an external Drive. I'm always doing this, and I've never had this problem before. I was able to import a number of pics and videos during that session, when the problem suddenly happened. Then I tried to import several times more and couldn't, not even pics. I restarted image capture, restarted the phone, restarted computer, used different cables, but the problem persists. One time, I was able to still import pictures, but as soon as I tried a video, I got the error message again. Then I turned everything off overnight, tried a video, which worked, but when I tried a second one, I got the error message again. So, it's a bit inconsistent. What can I try to do? I'm always using image capture, and I've never had any problems before. I did not upgrade the system, either.