Mouse Scroll Wheel Stops Working After Viewing PDF

[betapro]

Hi, I have a small SPA (full screen) HTML app that opens PDF files with Sumatra when a link is clicked. Before the PDF file is opened in Sumatra, the mouse wheel is able to scroll through the HTML page content. After the user has finished viewing the PDF file and clicks on an HTML "Back" button to return to the previously viewed HTML page, the scroll wheel no longer works. However, if the TAB or F6 keys are pressed, functionality of the scroll-wheel returns immediately. Is this a bug? Bear in mind that when opening another PDF file, the scroll-wheel will still work with a PDF file, but will not work after returning to the HTML page content. Is there a way to get around this without the user having to press the TAB or F6 keys?