To make it easy for folks...
"Ruger recently discovered that all Mark IV™ pistols (including 22/45™ models) manufactured prior to June 1, 2017 have the potential to discharge unintentionally if the safety is not utilized correctly. In particular, if the trigger is pulled while the safety lever is midway between the "safe" and "fire" positions (that is, the safety is not fully engaged or fully disengaged), then the pistol may not fire when the trigger is pulled. However, if the trigger is released and the safety lever is then moved from the mid position to the "fire" position, the pistol may fire at that time."
I have "Volquartsen'd " one of my MKIIs.It shoots extremely accurate, and with the Volquartsen kit, the trigger pull is 4.4 lbs and no slack. It is finicky about ammunition. Doesn't seem to like Federal.
They are for sure owning the defect, but the mistake began with the MKIII, lol.I put an amazing amount of rounds through a Mark I and then gave it to my son who continues to enjoy it. It's one of the finest pistols ever made, BUT even after cleaning it hundreds of times, I totally dreaded putting it back together. The Mark IV fixed that problem, but now they found an issue with the safety. Ruger owned up to the problem and they've recalled the pistols for repair. Those who have been around long enough will remember that Ruger did a huge safety recall on their single action revolvers some years ago. (As a contrast, look how many decades it took Remington to own up to the problem with their 700 series rifles!) Ruger has also volunteered to give each person getting a pistol updated a free magazine. That's a fair deal from an honorable company.