Vis.js hoverNode not triggered

Question

There is a graph using Vis.js Network that consist of circles and edges between them.

Hovering mouse over a circle is supposed to show a tooltip.

Using Vis.js hoverNode and node.title (for tooltip content).

When mouse is moving from empty space into a circle - it always works:

However if mouse if moved over the edges neighter hoverNode nor 'blurNode` every triggered:

Is this a bug? Are there any possible work-arounds?

Mercenary

Did you ever find a solution to this? – Derogate