Duplicate draw.io diagram tab gives "Illegal Constructor" message

Question

I have a diagram with 2 tabs names "Option A" and "Option B". When trying to duplicate wither of the tabs I get a popup stating "Illegal Constructor".

The message in the popup is different depending on which browser I use.

Chrome: "Illegal Constructor"

Safari: "function is not a constructor (evaluating 'new a.constructor')"

unknown · Answer

That C4 extension is not written properly, you should not use it.

bjorkblom · Answer

I have the very same issue. I'm using a plain draw.io setup but with the C4 extension (https://tobiashochguertel.github.io/c4-draw.io). I cannot duplicate, copy elements nor tabs in my diagram.

The issue occurs in the browsers that @JD Stuart explains as well as in the Draw.io desktop application. I'm using OS X.

unknown · Answer

This is using the latest draw.io plugin for Confluence Cloud? What browser/version and OS are you using?