What factors can cause established controls to lose effectiveness?

Established controls can lose effectiveness due to changes in the operating environment, such as new technologies or processes that weren't anticipated during their design. Additionally, employee turnover or inadequate training can lead to inconsistent adherence to controls. External factors like regulatory changes or evolving threats can also diminish their reliability. Finally, complacency or a lack of regular review and updates can result in controls becoming outdated and less effective over time.