A DA/DAO revolver can easily experience a functioning problem when the shooter doesn't allow full trigger recovery. Totally shooter-induced. Short-stroking the trigger.
When people try to modify or fiddle with the action of their revolvers they can also increase the potential for a range of problems to occur, including light strikes, stubbing, failure of triggers to recover, throw-by, carry-up, etc.
Not properly maintaining one can result in increased potential for functioning issues, like ejector rods coming loose (on some models), extractors not fully seating (debris underneath), etc.
Improper (including abusive) handling isn't without potential for possibly resulting in a mechanical issue, like someone "flipping the cylinder closed", instead of closing it properly.
Using lesser quality or improper ammunition can also result in potential problems, such as bullet pull (jumping the crimp under recoil), an obstructed bore, accelerated flame cutting/erosion (titanium cylinders), just to list a couple potential issues.
Revolvers are very reliable, when properly maintained in good condition and used with appropriate, good quality ammunition ... and especially in the hands of a trained and experienced revolver shooter.
I still use a number of my J-frames as occasional retirement weapons, and they see a good deal of range time for quals, drills, training, etc.
As a S&W revolver armorer I keep things simple and keep them running within normal spec. (Okay, closer to the top end of normal "spec".
)
Being a long time revolver shooter, and someone who carried a service revolver for the first several years of being a young cop, I consider the modern revolver to still be a viable firearm for many personal defensive roles.
I miss the days when most people who carried handguns had to learn their foundation handgunning skills on DA revolvers. Now that small DA/DAO revolvers are enjoying yet another resurgence of interest among a lot of younger LE shooters, for secondary and off-duty weapons, it's often harder to upgrade their pistol-only based skills to help them become revolver shooters. I'd much rather make a DA revolver shooter into a pistol shooter, than the other way around. Less work.
As an armorer for S&W revolvers and a number of different make/model of semiauto pistols, I'd much rather support most pistols than revolvers, though. Easier.