Visual Studio 2017 code editing note for TSX files: column selection mode with Alt+arrow does not always work

I've recently used Facebook's React front-end technology a lot, and it complements well the regular C# ASP.NET backends I write. React contains a nice feature called JSX to support creating view components, and in the TypeScript world, you can convert these JSX files to use TypeScript syntax, allowing you to write in TSX syntax.

However, I've noticed that even the latest builds/updates of Visual Studio 2017, sometimes the Alt+Arrow keys code editor column text selection feature stops working. If I switch to C# code files (.cs), the same rectangular area selection works just fine, but when editing TSX files, it does not.

So far, the only remedy I've found for this is to close the file and re-open it again, or, if that won't help, restart Visual Studio. Even though this is not a perfect solution, it gets the highly useful editing feature back alive.