I see this issue addressed on github but I am still not 100% sure what the fix for this issue is. From what I understand it is a problem with unCSS stripping dynamic classes out of the css because they are not there when the build process runs. Both work perfectly when running browsersync with the src folder, but break in dist.
Here are a couple threads talking about it:
If anyone here could point me to a fix it would be much appreciated!