Version 63.0b3 right now, first noticed this in the update that introduced ‘Left-align Viewport’ in responsive mode.
After a while of working in a tab with the inspector open it will stop loading CSS in. Seems to happen pretty consistently, I’ve been disabling add-ons until I’ve just had RES and Vue Tools open now and it’s still persistent.
Opening a new tab will return things to normal, refreshing doesn’t.
Otherwise, I love what you’re doing!