Hey @tiffany! Based on the videos you've shared, it looks like this issue persists even in a brand new app. Is that right? Also, are you running a self-hosted instance of Retool?
Under the hood, that particular component is powered by FullCalendar, which loads its own font. There's a note in its source code that specifically calls out the possibility of having those styles overwritten.
If not an extension, it's also possible that any branding or theming you've configured within Retool may be causing a conflict. 