Auto mode not working after 2 waypoints!

hardware- f450 quadcopter with apm2.6 with ublox neo7m gps and 3dr clone telemetry module
firmware version-ac3.2.1

i am having troublewith the auto mode. Normally if i dont use the auto mode, loiter and rtl functions perfectly well. But in auto mode, after performing 2 waypoints, the drone seems to lose its way and oscillates up and down near the second waypoint. At this condition, when i switched the flight mode back to loiter, the copter was not under my control anymore. it kept on moving up and down and sideways as well with no control on my throttle, pitch and roll. Only the yaw control was with me. Why is this happening??? why doesnt the quad switch back to loiter even after i switch modes? Stabilise mode seems to work.

When i checked the flight logs, it showed a radio_failsafe error even though my flysky th9x was very much within control range. And the error triggered a RTL as well, but the copter dint at all perform any RTL, rather stayed where it was.

Any help on this issue would be highly appreciated as i have been having this trouble for quite sometime.

Everytime, it performs only 2 waypoints. and doesnt switch back to loiter from auto!
PS: when i switched back to stabilise from loiter, i lost control and one prop broke mid flight and crashed my drone

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You’ve got RTL final set at 7 metres instead of zero.
I always ran my APMs with compass learning off,or zero.
Your waypoint down speed is set way lower than stock (100 )
I always set this to 20.Just in case of corruption (I’ve seen it a few times)
RTL has a 5 second hang and is set at just over 11 metres.

Personally I’d reload firmware and recalibrate.I can’t see a reason for the mission not working but it isn’t.The radio looks very flakey and could do with checking out thoroughly.