Since a recent update (using the beta app) I've been experiencing a bug with the new menu bar on both a Pixel XL and Pixel 2 XL. The first time I tap the "+" symbol to open the menu bar, it opens a blank bar without the icons. If I then close and reopen it, the icons appear. I'm unclear what resets the bug, as it happens to me several time per day, but switching between apps or sleep/wake-ing my phone doesn't reliably trigger it.
The problem was happening on my Pixel XL for maybe a week. My Pixel 2 XL was brand new today, so it doesn't appear to be install related. Both phones on the latest android and security patch.