I'm using Semantic-UI-React in a very simple front end. The main page is using a Sidebar.Pushable to show a menu and the main content. If any of the sub-components opens a Modal, the Sidebar stops reacting. No error - I assume it's something to do with some CSS irrevocably changed at some level. Once a Modal is opened anywhere in the app, the only way to get the Sidebar to be pushable again is to reload the page.
I did my best to drill into the CSS, but I'm still missing it. There's an ancient issue on Github, dealing with similar behavior in semantic-ui itself (i.e. no React involved), but no conclusive solution.
To recreate, just use the code from the Sidebar example, and add a button that opens a Modal in the Pusher. Once the Modal is open, the Sidebar is dead.
I've created a Sandbox sample.
Update: opened a Github issue: https://github.com/Semantic-Org/Semantic-UI-React/issues/4110
Looks like this has been fixed in semantic-ui-react@2.0.3 🎉. See this issue for details.