I use two cameras: a Nikon d750 and a Nikon d850. I have recently started using RAW format in slot 1 and JPEG format in slot 2 as backup. The 850 takes great photos, but the files are huge. One photo I was looking at yesterday was 61 megabytes. That adds up in a hurry.
I have been using Adobe programs to process the pictures: Bridge, Lightroom Classic, and Photoshop. I also have a free software program called FastStone, which is pretty good for some purposes but not as powerful as Adobe products.
However, for the last 2 or three months, when I open files in Bridge or Lightroom, about 5 to 10 percent of the files appear damaged, with multi-colored horizontal lines obscuring parts or all of the picture. The same pictures look fine in FastStone. These damaged pictures do odd things. Sometimes the thumbnails in Lightroom or Bridge look good, but when I open them to develop them, they look good for a second or two and then go bad. Sometimes a picture will look good during one work session and then bad during a subsequent session. I have also called up old pictures from 2014, before I began using Adobe products. These pictures have always looked good, but now a few of them are corrupted.
I have talked to camera people. I bought new sd cards with faster read/write speeds (300/299 mbs). That made no difference. I bought a new sd card reader, upgrading from 2.0 to 3.0. That made no difference. I have started downloading directly from my camera with an hdmi cable. That made no difference. I have tried downloading directly to Onedrive. I have downloaded through Bridge and Lightroom. I have downloaded using Nikon Transfer software. Nothing makes any difference.
I have had online chats with Adobe customer reps on two occasions. They made some adjustments to the software. The problem persists. Adobe's latest theory is that my external hard drive, where I store my pictures, has some flaws. Adobe recommended that I backup all of my files and then reformat my external hard drive. I'm not sure that is the right solution. Another person theorized that our monitor may be the problem. But the monitor works well for everything but those few pictures.