Using gparted to clone a drive: errors

I have an old MacBook that's stopped responding. Ruing Disk Utility in target mode asked me if I wanted to repair the disk, and then it stopped responding. I didn't repair as I was worried this could delete data I wanted to save.

I've removed the hard drive, put in a case, and coected it to my Ubuntu computer. Files all seem to be visible in the GUI, though it has seems to problems opening both iPhone and Android photo uploads. With gparted, I've started copying this drive to a partition of an exteal HD. I got an error message at the begiing, but I pressed on. Now, I get waings every 20 mb: "Input/output error during read on /dev/sdb" which ignore because i don't want to abort and because retrying doesn't do anything. I'm at 440/476.6 GB progress now, but I don't know if it reflects things that will actually complete, and it's excruciating clicking away these error messages.

What are my options here?