I have a brand new Jackson JS30, and I am already having issues with a weird fluttering sound when I pull of from 15 to 14, 9 to 8, 8 to 7, etc. I can't seem to find anyone else with this problem, yet I have had this same problem on three guitars. I have tried it on multiple amps, and with different cords, as well as taking it to the shop multiple times. Here is a link to the sound. "https://soundcloud.com/porter-larson/fret-fluttering/s-p9y5f"
This may be a nothing burger, but distortions and beat frequencies can be caused by pick-ups too close to the strings. I had a similar distortion on my Peavey Raptor cured by increasing the distance. I don't know if this applies to Humbuckers, but for single coil pick-ups, a starting spacing of 2mm (at the e string) and 2.4mm (at the E string) between the pick-up's magnet and the bottom of the string (this from a video I watched on a Strat setup). Oh, if you have an electronic caliper for measuring, a cool trick to get that elusive distance between string and fret or string and pick-up is to measure the diameter of the string in question and zero the caliper. This now allows you to measure from top of the string to the fret or pick-up while reading the distance from bottom of string to the fret/pick-up. BTW, these calipers are really cheap these days! I just looked and Amazon shows them for as little as $9.99 (although I'd pay closer to $25 to get some quality) Neiko makes a decent one for $20 (Mine's a $150 Mitutoyo). Good Luck & Great Playing!