Is speaking about a colleague's negligence in maintaining devices, with the aim of preserving them from misuse, considered backbiting for which one is sinful?

Backbiting is a grave sin that the Sharia has warned against. It is to mention about your brother what he dislikes. It is not permissible except out of necessity, such as to remove injustice, to seek help in changing an evil, or to warn against evil.

It is not permissible to mention a colleague's flaws except for the benefit of work and what rectifies the situation. You must advise him on the necessity of safeguarding the trustworthiness of work tools, for "religion is sincerity (or good counsel)."