One of the users wrote on the forum, "I am not sure why, but the Pixel 2 XL screen flashes when unlocking (fingerprint and lock button), when the screen wakes up because of notifications, when the screen dims and the phone locks, and when manually locking". Turning off the ambient sensor is the temporary fix for the flashing screen issue on Pixel 2 XL. The tricky part is that Google doesn't have an official fix for the issue just yet, though some people commenting on the thread say that Google claims the problems are down to a software malfunction.
A small number of users, however, have reported cases of faulty olephobic coating on the Pixel 2 XL's screen. This was a breath of fresh air in a realm of Android complications, and Google followed this success with the Pixel 2. As such, the fact that mics on the Pixel 2, Galaxy S8, and Note 8 mysteriously aren't working has got a lot of customers quite irritated - and rightly so.
Google is having a hard time with the Pixel 2 and Pixel 2 XL flagship devices. With Google promoting the camera, these kind of issues are really disappointing to see, and a brand like Google has done it wrong this time with the Pixel 2 series.
Pixel 2 XL users have reported the issue on Pixel User Community. Owners of both the Pixel 2 and Pixel 2 XL handset are already being recruited to join a class action suit against Google, HTC and LG because of issues with the display on both phones. This could still be a hardware related issue that's directly tied to Android Oreo.
It doesn't happen on the Pixel 2 but only on the bigger variant.
Some users even have reported a odd screen flashing which happens when you lock or unlock the phone. However, a user shared in a recent post that the problem may be resolved by blowing into the bottom speaker. Doing this made my microphone work again and it continues to work when it goes out.