Once bitten, twice shy, so in the aftermath of my Glock K-boom, here's my answer to inadvertent double charging.
The Lee press has only 3 stations but I've found the priming part to be kind of spotty so I don't use it. This leaves 1 station open. Decapping and priming are handled separately so this setup does first powder dispensing, second powder checking, and third bullet insertion and seating.
The wood piece is a plunger that goes down through a powder dispenser die in a caliber I don't use. When the powder filled cartridge comes up it rises about 1/4" if it's correctly filled, and about 1/2" if it's gotten hit twice. Inside the plunger are 2 Lithium batteries and the wires from the bright blue LED seen hanging out the left side.
If the powder level is correct, nothing happens, but with an overcharge, the plunger goes up far enough that the bolt presses the led lead down onto the top of the battery stack illuminating the LED. The operators seating position is off to the left in this picture, and the LED is pointing pretty much right at my eye and trust me, this little baby is bright. The spring allows the device to catch anything from a little over to a lot over without jamming the press.
The drawback is that the device is bulky and takes up space that might be used for adjusting the powder reservoir. There is no doubt in my mind that this thing could be made to fit entirely inside a die with little more than the LED poking out, but that's for Rev B. Meantime I'll suffer.