Case I. Operational data field:
Create Problem (or Problems by severity) widget using API request. Use invalid value for Show operational data parameter.

"fields": [
                        {
                            "type": "0",
                            "name": "show_opdata",
                            "value": "9999"
                        }

Open created dashboard on frontend, observe Undefined index:

In version release/4.0 this bug is actual for "Show latest values" setting. If value is invalid Problems widget is eternally loading:

And undefined index in Problems by severity widget:

Case II. Dynamic setting:
Create Classic Graph (for example) widget with wrong Dynamic parameter:

 "fields": [
                        {
                            "type": "0",
                            "name": "dynamic",
                            "value": "999"
                        },

Open dashboard on frontend and observe that actually widget is not dynamic (Dynamic: false), but in settings Dynamic is checked (Dynamic: true).