radio controller lose its control ,after app control

when my GCS app controls copter, radio controller will lose its control. even if copter landed, controller cannot arm either. after re-plugin battery, the controller can control copter again. there is no such problem if using QGC controls. btw, my app uses only GUIDED mode when flying the copter.
please help me to troubleshoot this issue.

1: You cannot control your copter through radio when the copter work on GUIDED mode.
2: I guess your app always try change flight mode to GUIDED mode. You try to change flight mode through mode_ch (usually CH5) but your app change to GUIDED mode through GCS. (just my guess)

Please provide a log, it helps to locate your problem.

thanks for you answer.