First and foremost, a flash charge is when you do any attack (be it a normal swing/shot, a charge blast, or even a shield bash) when your attack speed changes; being Stunned is an example, and the Maskeraith Deadly Cloak and Drakon Frenzied Firestorm are another 2 examples. If you have good enough timing, you do a second attack identical to the first, except all the projectiles hit at once (for example, if you Blitz flash charged something, you'd do the normal 15 hits one by one, then a second barrage of 15 invisible hits would instantly and simultaneously affect the area again.)

Since each Blitz charged bullet can disrupt an enemy, 15 of them in the span of 1 tick causes quite a few glitches. Do it to the dummies in the Training Hall, for example. But I'm getting off topic.

In Shroud of the Apocrea today, my team mate was trapped by the Apocrean, and I already had a charged Blitz with the Maskeraith Deadly Cloak on. The Apocrean Harvester began to do the gaze attack on my team mate, and at that same moment, I unleashed my flash charge, disrupting the Apocrean when the second barrage of 15 bullets hit it. For some reason, the gaze attack visually remained, much like the old Seraphynx Aura graphical glitch. The gaze lit up the area quite a bit, and we were able to easily see where the Harvester was; that is, until I killed it accidentally and it respawned, no gaze glitch.