Quaternion/Look_At() issue: when invoked look_at() occasionally faces away from the target

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So what I am hoping to get is some sort of guidance on how to detect the situation and/or massage information so that look_at() works 'correctly'

Generally I think when the (euler) angles on an axis (in this case, x) get around PI or so, look_at() can arrive at the face away state.

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The nearest I can find is this conversion in order to cope with the dual representation of any orientation:

func test(q_Current:Quat, q_Prev:Quat):
	if(q_Prev - q_Current).length_squared()  < (q_Prev + q_Current).length_squared():
 	print("negate me")
 	else:
	 	print("retain me")

converted from this answer:

https://stackoverflow.com/questions/42428136/quaternion-is-flipping-sign-for-very-similar-rotations

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Which doesn't help.

lag here is "look at goal" = global_position_of_goal - global_transform.origin

lag (0, 0, -0.25) standardize prev (-0, 0, 0) to next (-0, 0, 0)

lag (0, -0.167456, -0.06437) standardize prev (42.053394, 0, 0) to next (-68.973297, 0, 0)

lag (0, -0.069461, 0.013233) standardize prev (-51.623997, 0, 0) to next (-79.214165, 179.999985, 0) <------! AUGH

the notable feature is that z is positive in the last case.

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So the simple solution (so far) is the geometric interpretation of look at goal z going positive is that the goal is now behind the object i want to have look at the goal since there are two representations for any orientation, and I want the object to go upside down to look backwards, look_at needs Vector3.DOWN instead of Vector3.UP as its 2nd argument.

hopefully a test of z < 0 and inversion of 'up' for look_at() is the entire solution for this case