These faults appear not to be caused by poor maintenance or neglect, but potentially as a result of poor workmanship, improper oversight and at times it seems, a disregard for building regulations.
Gallai'r rhain ddigwydd pan gaiff data ei gofnodi'n anghywir i systemau gweinyddol neu drwy gamgymeriadau mesur sy'n deillio o ddehongliadau anghyson o ddiffiniadau.