I've been trying to delete photos from subfolders of DCIM, but I keep getting an error "The device has either stopped responding or has been disconnected."

I copied all of my photos from my phone to my computer using windows explorer. Now I know I shouldn't delete the DCIM folder so I tried to delete the folders within it. However, every time I try i get the following error:

I've tried different USB ports, they all say the same thing. I was able to do this before so I'm not really sure why I can't do it now.