WPNAV_RADIUS set to 0 causes Copter to Loiter xx times at Waypoint 1?

Hi All

I am flying a quadcopter with AC3.5.4 , Mission 1.3.52 .

I do an AUTO Mission with WPNAV_RADIUS set to zero .
I plan a mission with first Waypoint [LOITER_TIME] with delay [3 seconds] and the second Waypoint set to RTL.

During Auto Mission , copter navigates to Waypoint # 1 and then loiters there for more than 60 seconds until i manually RTL it.
{ Copter should loiter there for 3 seconds and then Return to Launch } .
I have checked everything regarding this problem as i know , the only Parameter i change was i set WPNAV_RADIUS to Zero .
Is this the parameter that causes Auto Mission to stop at Waypoint # 1.

Kindly help !!!
If someone could explain why this is happening i would be very thankful.
( Copter would have crashed loitering there but thanks to the Telemetry connection that informs me ).

Why would you ask it to hit an exact point with perfect precision in all axes ? You are asking for sub millimetre precision.

I set this parameter accidentally.

I wanna confirm that setting WPNAV_RADIUS to zero causes Copter to halt at Waypoint.

So if it is true then next time i would be very careful about this parameter and even include this in my Pre-flight

Also i would like to raise this issue (in Github Issues Forum ) to add it as a Pre Arm Check like :
Pre-Arm : Check WPNAV_Radius Value .

One Question:
I have found this line in Releases Notes : Copter 3.5-rc7 25-May-2017

e) sanity check WPNAV_RADIUS is non-zero. "

Although i had no warning from Mission Planner about it.

You basically asked it to hit the point within 0.0000000m in all axis. It’s not stuck there, it just won’t hit it that perfectly.

It would be a ton of code to foolproof all parameters in preflight.

Beware of Mission planner, there are plenty of less … messy alternatives.

Ok. I understand this.

So from now on , i am adding this Parameter [WPNAV_RADIUS == 0] in my Pre-flight Checklist.

I had almost crashed my Copter due to this mistake.

Thankyou very much @Andre-K.