Sometimes imported files don't trigger Less to be transpiled

[PonchoPowers]

If I have a file which imports other files called Site.less, and when I update one of the imported file, the Site.less file doesn't always get transpiled to CSS. To fix, I have to restart Visual Studio. There are no build errors.

Take for example the following: Site.less

// lessc "../../../content/css/site.css"
@import 'Mixins.less';
@import 'Base.less';

Base.less

// no-compile
body {background: red}

Mixins.less

// no-compile
p {background: blue}

When Mixins.less is updated, will Site.Less isn't always transpiled and there appears to be no pattern as to why.