I've been experiencing this for months.

Moving or standing still, attacking or not, those don't seem to matter. All I've been able to nail down is that it happens when twisting, as opposed to say spamming manasong.

This has been happening to my bard for months, hell, over a year easy. It doesn't matter what song or what i'm doing, it will just randomly disappear. I've tested just about every combination of songs, sitting, standing, running, grouped, not grouped, different buffs, mask illusions, everything I can think of and it still operates the same way - sometimes it's there and sometimes it's not. It will be up for half a second and then randomly poof.

bump