Log0-Why user thread be blocked?

If your user thread be blocked you should read this post before set one issue to particle github.
We find one issue:
1.connect Photon to server
2.take Photon out of the signal range of router
3.User thread stop working
4.EXTI interrupt alive
Try to Fix it:
1.I think Maybe some API blocked
2.search firmware reference
3.I think I don’t call any synchronous system functions(I am very busy then)
4.It is a System-Firmware issue,set one issue
5.Actually I made a mistake at step 3
Try to Fix it again:
1.m-mcgowan Ask me to check if I have call any synchronous system functions
2.I removed all code in loop() except led blink part
3.test again,It works!!!
4.Use grep to search all code
5.I have call WiFi.hasCredentials() in loop()!!!
1.Minimize user code when you test one issue
2.Calm down even you are fall in many troubles
Thanks @m-mcgowan again!

Thank you for your helpful instructions!