拒绝访问属性"handleEvent"的权限

我正在使用Selenium 2.45.0网格在多个浏览器中测试一个Web应用程序.

I'm testing a web app in several browsers with the Selenium 2.45.0 grid.

在某一时刻(我想是将Bugsnag添加到应用程序中)，某些find_element函数在Firefox中开始失败(在Safari中仍然可以使用)，并显示拒绝访问属性handleEvent的权限错误."

At one point (I suppose when Bugsnag was added to the app) some find_element functions started to fail in Firefox (still work in Safari) with the 'Permission denied to access property handleEvent error.

似乎有一种解决方法:

adding 
$driver -> get_active_element();
before calling
$driver -> find_element...

但这很尴尬.

其他人是否也遇到过同样的问题并找到了更合适的解决方案?

Did anyone else face the same problem and find a more adequate solution?