A partner implemented a custom property. This property is basically a button that opens a dialog where I can select an object which is, in the end, saved as a long string.

The property works well in Chrome, but it does not work in IE11 or Edge, he gets the following error in IE dev tools:

In the _setValue method, we need to clone the value received from the dialog:

this._set("value", JSON.parse(JSON.stringify(val)));