1. Turn shadow DOM on
2. link a syntax theme, and make sure you're using that theme
3. atom -d in the syntax theme dir
4. Edit a stylesheet
5. save
6. The editor goes gray and is unusable

It looks like the height is infinitely growing:

Notes

• You can close that editor and everything is fine
• It only happens on the active editor when the window has focus. Change the file out side of atom with atom not focused, and it's fine.