Keyboard access is trapped in Flash object
Keyboard focus MUST NOT be locked or trapped in a particular page element and the user MUST be able to navigate to and from all navigable page elements using only a keyboard.
Sometimes custom widgets, plugins, embedded applications, and other content formats can create a keyboard "trap" where the keyboard focus gets stuck in one place or within a widget or application. Keyboard traps can make interacting with web content extremely difficult or impossible for keyboard users. Keyboard users must be able to move into, and away from, any user interface component, simply by using their keyboard. When keyboard traps are removed, people who rely on a keyboard will be able to access all of the otherwise-accessible content.
Flash objects may trap keyboard focus. Chrome, Microsoft Edge, and Safari all block Flash, and Firefox will disable Flash in 2019. Adobe itself will end support for Flash in 2020.
Fix this issue by using HTML and web technologies instead of Flash.