Google's new Pixel 3 arguably has the best camera on an Android phone (or any phone) in 2018. An issue has been discovered by multiple users, however, where a photo fails to save after the shot on both the Pixel 3 and Pixel 3 XL . This particular issue has been reported since the Nexus 5X and 6P days, so it's not a new problem. Similar complaints have surrounded recent Samsung phones like the Galaxy S and Note series, so it could be a Google Photos issue as well.
The Reddit Community has been vocal about the Pixel 3 issue for the last couple of days and many users have complained on the Google Product Forums as well. So Google is likely aware of the potential bug at this point.
Many users have offered theories and possible fixes. Some claim that a photo won't save if the camera app is closed or phone is locked right after the shot is taken. That could simply be a matter of a disruption to the picture's processing. Others claim that disabling Android Doze solves the problem. The issue shouldn't happen at all, of course, and hopefully Google can fix the bug with a software update should it become widespread.
Source: Android Authority
You also don’t have Google’s memory optimization on a Samsung, software/hardware bugs happen all the time – extensive testing will never find them all.
I don’t remember any Pixel’s batteries blowing up or catching fire. I’ve never had that happen on any of my Nexus devices.