A calibration is an important step when using PhotoModeler, especially when looking for maximum accuracy.
A calibration usually is fully automated and requires no intervention, but if you’re looking for maximum accuracy, and the benefits of improving the calibration would outweigh the benefits of optimizing ALL project factors (as shown here: Factors affecting accuracy in photogrammetry), this article describes a few tips to take a calibration from OK to good.
So, if all other project/accuracy factors are optimized (ie number of points, photos, angles etc), then you might want to try to redo and improve the calibration, bearing the following in mind:
In summary, there are two main causes of calibration problems: a) the calibration grid or points move or change between photos (e.g. not fixed to surface); or b) something about the camera changes between photos (e.g. zoom/focal-length, or in some cases focus).
Many of these issues are subtle, but can have a detrimental effect on a calibration.
Also, if in your real-world project you intend to use Field Calibration, you may not need to fully optimize a calibration since the calibration may be a good enough starting point, and the Field Calibration process will fine tune and improve the solution. Information on Field calibration can be found here: What is Field Calibration?.