Not exactly sure what causes the pops on atomizers, maybe a bit of a hot leg? Anyhow, I have a Delta II, bought an RBA head for it, tried the included build, every single time I would pick it up, Bang! but only on the first puff, and only after it sat for a minute our two. Kinda why I'm thinking hot leg. Resolving was easy, build a new coil, rewick, has not done it again since.
Since you reduced the amount of cotton, possibly you have a tiny bit of coil that has poor contact with the wick, I'd do a rewick again, if that doesn't fix it, I'd recoil, and wick again.
Nice troll dragon! I may get one a little later, like them! You do know Joyetech has an upgrade available for the firmware, guess it adds some features, think it was just released so yours may not have it yet.