I haven't been able to reproduce this - it shouldn't happen, because the title attribute should be removed when the tooltip is created. I've made a minor code change that might fix the problem, but in the meantime, are you able to consistently reproduce this? Using what browser?
Yes it's consistent for me. I tested in Chrome (latest) and explorer 11. Windows 7 and 10.
It only happens on the first hover, after moving the mouse away and then hovering again, I no longer see the default tooltip.