Release : 12.1
Component : CA OUTPUT MANAGEMENT WEB VIEWER FOR ALL PLATFORMS
This isn't a Web Viewer application problem. Make sure you are using only IE11 in compatibility mode to run the 12.1 Web Viewer at Build 208 and below. Build 209 or later is required if you're using a Chrome or Edge browser as that is where the modal dialog support for those browsers was added. Based on the statement, “The issue does NOT occur if they perform the export on the laptop's built-in monitor.” this problem would have to be fixed either with Dell or with Microsoft.