Help Data seems to turn off randomly

[Colmss]

Hi,

recently I am a little confused with my data connectivity.

Especially when I use WhatsApp it often happens that I receive messages only when I wake my phone up from sleeping. But then it turns out that the message was sent minutes ago and the phone didn't signal it.

I think it usually happens on WiFi but Advanced WiFi is set to

Keep Wi-Fi on during sleep: Always
Avoid poor connection: yes
WiFi optimization: yes

What could be the problem?

 

[colchiro]

Battery saving apps like Juice Defender will turn off data and I read the other day where some texting apps don't work over wifi (supposedly a Verizon bug).

Otherwise a poor signal (wifi or 3g/4g) could cause similar problems.

 

[Colmss]

Okay, I just observed the behavior and when I wake up my phone I can see that the WiFi symbol is gone but the cellular symbol is grey.

Then WiFi pops up disappears and pops up again, connects and then I receive messages.

I don't have battery saving apps. Why does WiFi turn off?!