Log2:Why uart(Serial1) not work after call Particle.connect()?

If your uart(Serial1) stop work after call Particle.connect(),Please read this post before set one issue to particle github
1.I am starting a new project with Photon
2.Copy one demo from user/application
3.add my code
4.test uart with one pm2.5 sensor,work well
5.Add Particle.connect(),WiFi work well
6.After days,Can not get data from pm2.5 sensor
7.Remove function one by one,uart works without Particle.connect()
Find Macro define #define USE_SERIAL1 1 in ./system/src/wifitester.cpp
8.What!!!Set one issue
9.I should not add(actually it is from the demo)
Thanks m-mcgowan!!!

Thank you for your helpful instructions!