So, i've had my Buzz Bee Double Shot (specifically the Walking Dead variant with the side-by-side barrels) for about a few months now.
Lately i've been having trouble with the blaster either not priming properly, or just flatout not working with certain darts (it refuses to prime properly with my Buzz Bee Long Distance darts. inb4 someone goes "the darts are so bad the blaster doesn't wanna use them"). And on top of that, the right barrel doesn't seem to work as well as the left one, usually firing softer than normal.
The blaster works fine with my other darts.
I have taken it apart before (though not completely. I took it apart so I could at least peek at the internals out of curiosity), and I've used it frequently in the past.
My only guess is a combination of both of those things causing the blaster to not function right.