Camera pose worse after refinement with bundleAdjustmentMotion

Dear helper,

I tried out the new function bundleAdjustmentMotion released in Matlab R2020a to refine my estimated camera pose. The problem is that the output shows that the refined pose has a greater reprojection error than the imput pose. I thought the algorithm would rather not update the pose at all in that case.

Any clues why this is happening? And maybe what I could do about it?

Thanks in advance!

Below I have an example for when the problem occur:

worldPoints = [-103	-51.5000000000000	66.9500000000000
                -89.6100000000000	-61.8000000000000	66.9500000000000
                -110.931000000000	-51.5927000000000	50.9232000000000
                -91.0314000000000	-62.0575000000000	41.9519000000000
                -115.349700000000	-34.3711000000000	72.3060000000000
                -57.9272000000000	-59.2765000000000	78.0122000000000];

imagePoints = [150.922203055741	246.412460609795
                139.762086448905	245.010922434622
                152.832425559090	223.276361281141
                139.764208894823	215.907977399472
                171.702432806430	252.975377257368
                141.744415386340	256.777077665036];

worldOrientation = [-0.0561788573583534	0.998364830627578	0.0105641351693954
                    0.164654663131831	-0.00117174603335630	0.986350581142515
                    0.984750109365240	0.0571514827209302	-0.164319597516384];
worldLocation = [-339.652024249253	-35.6979662479237	56.9638605186294];
absolutePose = rigid3d(worldOrientation, worldLocation);

% Camera Matrix
c_xy = [186,186];
f = 281;
camera_matrix = [f,0,c_xy(1);0,f,c_xy(2);0,0,1];
cameraParams = cameraParameters('IntrinsicMatrix',camera_matrix');

[refinedPose, reprojectionErrors] = ...
    bundleAdjustmentMotion(worldPoints, ...
    imagePoints, absolutePose, cameraParams,...
    'AbsoluteTolerance',1e-9, ...
    'RelativeTolerance', 1e-9, ...
    'MaxIterations', 300, ...
    'Verbose', true);

Output from the code above starts and ends with:

Initializing bundle adjustment solver ...

Starting Levenberg-Marquardt iterations:

Iteration 1:Mean squared reprojection error: 5.1853

...

Iteration 69:Mean squared reprojection error: 4.2495

Iteration 70:Mean squared reprojection error: 4.2492

bundle adjustment stopped because the relative change in the squared reprojection error was less than the specified relative tolerance value.

Mean reprojection error before bundle adjustment: 1.4443.

Mean reprojection error after bundle adjustment: 1.6822.