Thank you for the clarification.
After research, we were able to pinpoint the cause of the issue.
Time ago there was a request in the Material UI for a feature called (TrapFocus). What this feature does is to prevent an element outside of the Dialog to get the focus. And in our case, we are rendering the Calender inside a Popup which is in the body element directly(outside of the Dialog). This causes the TrapFocus feature to return the focus to the Dialog, which on the other hand is firing the blur event of the Popup and the DatePicker is closed.
In this case, we can suggest two approaches:
1) Set a custom Popup to the DatePicker, and use its appentTo property to render the Popup inside the Dialog, so the TrapFocus function is not executed:
2) Check with the Material UI community if there is an option to disable this functionality.
I hope this is helpful.
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