Game Mechanics: Song cast bar

[Xaleban]

I'm not sure if this has been reported or if is just me. I have been having issues on my bard where the song cast bar randomly disappears. I have tested many different situations to see if its something particular that causes it. From what i can gather it does it more in combat than any other time. Its extremely frustrating because the song actually continues to cast even tho the bar vanishes. But reflexes cause me to restart the song because it appears the song has stopped casting. Youre help is appreciated