Every other time killed by a Ravager, it disappears and is invisible until it kills you again.

However, the Ravager can still be heard, and it will attack you as if it was visible. If hitboxes are turned on, it seems that the Ravager's does not exist. I wasn't able find if I could hit it, but I assume not.

Attachment 1 (Minecraft 19w05a 4.2.19 05_50_29 PM.mp4): A video of the phenomenon in action. (Sorry for the low quality, I had to compress it to less than a fifth of its original size due to the upload limit)