Thanks for writing to us. Can you please confirm the Dw and OS version details. Also, please try resetting Dw app preferences by following the steps mentioned in this KB article and let us know if the issue gets fixed on your machine.
Are you by any chance using a 3rd party extension called FlexiMenus by ExtendStudio? I would get rid of it. As far as I know, it hasn't received any attention in several years. According to their website, the developer quit making extensions for Dreamweaver.