I have found an odd case where, while on wifi, the data connection drops. When this happens, the phone remains in this broken state until you disable and re-enable wifi. For a while, I didn't even know when this problem would happen. Then, I would think "why didn't I get that email?" I would toggle the wifi connection and suddenly, tons of pending data accesses would occur. I installed an app to periodically ping a host to see if I am online (https://play.google.com/store/apps/details?id=com.hostpinger) and I found that it almost always happens overnight and sometimes during the day at work.
Has anyone seen this issue? I tried to enable the "Check of Internet service" feature under wifi advanced settings but that actually made the issue occur more frequently.
I have tried restarting and safe mode. The problem still persists.