The problem is that after the first round fires, the shooter’s reaction to the recoil is to grasp the gun as hard as they can. The recoil pushes the gun back far enough that the trigger resents, and grabbing it inadvertently pulls the trigger a second time. This can happen with a lot of high-recoil-low-mass handguns, and is part of the reason many people don’t like ultra-light .357 Magnum revolvers.
These early reviews make me wonder if DoubleTap didn’t bite off more than they could chew. Some cartridges just aren’t at all suited for such small, light guns. A version in .380 ACP might be a lot more popular, even if there are a whole lot of small .380s on the market. In any case, it’s a new product, and new products often need tweaking.
After all, their once-partner Heizer Defense, decided to go with .410 shot for their pocket pistol. It may be a single-shot derringer, but given that most .410 loads are on par with .38 Special from handguns, it’s safe to say that their model is probably easier to shoot.
And there’s one other thing that may need consideration: that the day of the derringer might be behind us.