Phone: stock 5.0.2 Moto E 2015
Randomly one day about 2 weeks ago I started getting popup notifications like:
Unfortunately, Keep has stopped.
Same for Pocket, and Google Play Newsstand. Like, regularly. In spurts. Like one after the other. Disabling the apps in preferences and force-closing them makes no difference. Resetting them to factory or removing & reinstalling makes no difference. Trying to open those apps directly also leads only to that error.
At the same time I noticed that I could no longer click on notifications from Inbox and Hangouts. I could open the apps directly but they would stop as soon as I clicked on a conversation. I then tried and saw the same behavior with the older Messaging and newer Messenger. I see similar behavior with Calendar and Play books -- i.e., I can open the apps directly, but as soon as I try to open an entity (an event in Calendar or a book in Books), the app stops with the same dialog as above.
Clicking Report in the above-mentioned popup always led to a crash ... until this morning. The feedback app now works.
What else works: Chrome, Google Now, Play Music (I use it all day every day), and the Contacts/Phone apps all seem fine.
PS: This is the same phone I had to do a factory reset on after after a routine reboot, Google Play Services disappeared on stock 5.0.2 Moto E 2015 unexplicably happened. Based on this, I'm starting to think that the flash memory is faulty and leading to random corruption. It's the only theory I've got.