I've had the stuck before climbing ladder bug, there are no bugs in console, but your webwalking event terminates and then attempts to start again in the same spot over and over again, which causes the bug.
I've noticed this occurring on x:3755, y:5672. There may be other positions that it happens in, but at least here the webwalk event does not stop looping.
Thanks for the script!
Edit, just produced the bug again in x:3753, y:5673,
x:3754, y:5673,
x:3754, y:5672,
x:3756, y:5672.
Not sure about any other places, just looks like you need to revise the webwalk break condition.