I have found the solution to this problem for all others who run into it.
As of Godot 4.1 "SpringArm" treats the character controller body/collision that its attached to as a possible collision for whatever reason. This may or may not be a bug, though I suspect it probably is when you consider how inconsistent its behavior is. The character must be moving quickly for the collision to take place, as well as only at specific camera angles does the collision happen.
In Godot 4.0 and previous versions the SpringArm node automatically ignored the character its attached to and ignored all self-collisions.
In a nutshell: Godot's built-in SpringArm is colliding inconsistently with the collider attached to the character.
The solution to this problem is to force the SpringArm to ignore collisions with itself and everything else within its root hierarchy (all ancestry up to the root node of the character).
On process ready in the root node for your character add this code:
First reference your SpringArm3D (drag and drop from the tree for its location), then add the
.add_excluded_object(self) modifier to that. "Self" in this case is a reference to the root node that the script is attached to, that may change depending on if your character script is on the root node or not.
Hope this helps anybody with the problem.