How to reproduce:

• Create a validator to easily generate warnings on content modification (only server side warnings)
• Add this custom validator to a content type's attribute
• Modify a content of this type
• Add a value that will generate a warning according to your validator
• Save
• There is a dialog box with the warning => OK
• Click on no button to not save your modifications
• The field in form is marked with a visual warning => OK
• Save again
• A dialog appear with the warning => OK
• Click on yes, to bypass the client side warning
• Another dialog appears with the same warning after server checks => KO