The interactive drawing has the secondary ellipse and the lower southern shaft highlighted, and the Earth's axial tilt is set to its correct astronomical value.
The object information panel for the lower southern shaft shows the geometric line angle fluctuating between 39.473° and 39.587°.
Because the length of the geometric line that forms the lower southern shaft is dictated by its angle, in the ratio of 221 cubits to 1 radian as explained in the basic section, then the length of the shaft must also be fluctuating. If you zoom in on the end of this shaft you can see how the architecture has been designed.
The height of the shaft is carved out of the stonework by the position of the geometric line as the principal ellipse rotates, just as with the upper shafts.
The length of the shaft also has a minimum and maximum value, the minimum being marked off by the polished back face of the door and the maximum value being marked off by the end of the shaft behind that door. If you look at the object information panel for the shaft, and compare the maximum and minimum lengths of the geometric shaft line, you will see that the length difference is 79.910 - 79.680 = 0.230 m.
The following illustration shows the dimensions of the end of the shaft that were reported in the Journal of Field Robotics article published by the Djedi engineering team who carried out the robotics investigation in the shaft.
The door at the end of the lower southern shaft, which I shall call 'Door 221', is not just a piece of plain stone. A dimensionally correct image of its front face is shown below and there are several interesting features which are indicated on the right side of the illustration.
These features contain information which helps to solve other parts of the pyramid's design later in this work.