Group Clipping Broken When Using Corner Radius

I noticed clipping is broken on the official example for Group marks. To recreate:

1. Load example: https://vega.github.io/vega/docs/marks/group/

1. Enable clip and note the internal rectangles are clipped

1. Reduce width to see clipping still works

1. Adjust corner radius to anything and then back to zero

2. Increase width again and notice the internal rectangles are no longer drawn properly