A dogleg in elevator installation can occur due to:

A dogleg in elevator installation refers to a situation where the elevator shaft or guide rails are misaligned, typically resulting in a bending or deviation from the intended vertical trajectory. This misalignment can create challenges for the smooth operation of the elevator, impacting safety and efficiency.

The choice indicating crooked welding of the casing or drilling errors as causes of a dogleg accurately highlights a critical aspect of installation. If the casing of the elevator is welded at an incorrect angle or if drilling for anchor bolts or brackets is done inaccurately, this can lead to a misalignment of the guide rails. Since the guide rails are essential for the proper vertical movement of the elevator car, any discrepancy in their alignment can lead to a dogleg condition.

In contrast, cabling issues, improper structural support, and poor maintenance may affect other aspects of elevator performance, such as ride quality or operational reliability, but they do not directly lead to the type of angular deviation defined as a dogleg. Therefore, the inaccuracies in welding or drilling related to the casing are the precise faults that can cause the structure to not achieve its intended straight alignment, making it the correct answer.