In AEM Forms designer while running the scripts or when navigating to the XML Source tab and attempt to scroll through the lines of xml , 'unknown bravo error' is observed. Post this error , Designer window show mostly blank and all buttons at the top of the screen might flash quickly. The Design View/Master Pages/XML Source tabs at the top of the screen will disappear.
Resolution or workaround: This issue might be coming due to other software service conflict. The software is "Pharos Systems Print Scout Service". After stopping the service of this software, designer worked fine and no unknown bravo error is observed.
This is one of the solution or workaround. There might be some other where the service would not have to be stopped. If there is any please let us know, would be very helpful.