Proverb, quote or phrase which convey that the approach, ideas that are meant to improve the system or process are the onces which fail them [duplicate]

I am looking for a proverb, quote or phrase describing the processes (or structures or ideas) which are supposed to bring in efficiency, enhance the gaps and increases in-efficiencies, but instead prove to be the reason for the decline of a system.

Explanation with example

Big external agencies were hired in order to define the efficient way to improve the system. However, these agencies do not understand the system and do all sorts of trial and error methods to innovate the process for years, yet not only do they waste company resources but are paid a ton of money so as to fix what can be done internally.

The road to hell is paved with good intentions? Is 'devil in diguise' too harsh? Neither of those are a great fit. Of course the Germans have a single word for it, but this is the 'English' stack exchange. Here it is in German, if that helps: Verschlimmbesserung.

That which protects, sometimes infects.