I have had failures in both.
The semi autos were easier fixes. Two squibs from bad factory ammo at the range. One was worn out spring that was replaced when I got home.
The revolver required a gunsmith. The spur on the hammer of my Model 67-1 S&W broke. Luckily the gunsmith had the part for it there. Half an hour later I had the gun back. Once while shooting the Anaconda I had a factory round that jumped crimp, and tied up the cylinder. It took a bit to get the cylinder open without bending the crane, or dinging the cylinder. I chalk that one up to bad ammo.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.