Sorry, I had missed this one.
Yes, I have fixed this in the latest cut on the code - not yet released.
In gauges.js, towards the end, look for...positiontooltip: function ($, $tooltip, e) {
Just before the last line of that function add the following (previous last line included below)...
// last ditch attempt to keep the graphs 'on page'
x = Math.max(x, 0);
y = Math.max(y, 0);
$tooltip.css({left: x, top: y});
See if that works any better...