css transition outside rc-animate not triggering #22

I'm creating a dropdown/collapse that has 2 animations when clicked: 1. an arrow that rotates 2. the content slides open/close. The arrow animation is triggered using pure CSS and the sliding content is added/removed to DOM so I use rc-animate. The issue is that the arrow doesn't animate in Firefox but it works in Chrome/Safari.

Here is a runnable example https://codesandbox.io/s/Wn5j4G9Qv

OS: Mac OS X Sierra
Firefox 52.0.2 (64-bit)
Chrome 57.0.2987.133 (64-bit)
Safar: 10.1