Disappearing Buttons

Not sure if this is a known issue already or not, but I just had the "disappearing buttons" soft lock happen in a GAC fight using LV + Appo and CX2 vs PKHO + Vane and FDC (it was a cleanup).  It happened when he killed the summon for the first time.  There were no attack buttons, but nothing else was happening either.   The timer still counted down though.