Hi. I'm running Lightroom v5.7 on Mac OS v10.11. I am downloading photos from a two Canon 1DX's shooting JPEG images. Downloads of 1000 images used to take less than 5 minutes (I never precisely timed it). Down loads, for both cameras now take in excess of 20 minutes, if it completes at all. What can be done to resolve the lengthy download issue. Thank you in advance.
Please click on the below link to update Lightroom.
Once done, check for the issue.
Let me know if this helps.
Your card reader (or other transfer hardware) is malfunctioning. Try different transfer hardware.