I'm almost ready to take my 3DR hexacopter out for a test flight, but I'm having an issue with motors 5 and 6. Channels 1-4 coming out of the APM (version 1) seem to be working fine. In stabilize mode, I can arm the ESCs and motors 1-4 will work. The ESC on motors 5 and 6 emit continuous beeps, which indicate that the throttle position isn't all the way down. If I switch motors 5 and 6 to APM outputs 1-2, they work fine, which seems to indicate that I have the ESCs calibrated correctly. I have updated to Hexa version 2.5.4, and I am currently using the "+" configuration. Any ideas why channel 5 and 6 coming out of the board would be emitting a PWM above normal, triggering the fast beeps from those ESC's?