The work is not ready while its success still depends on someone remembering an unexplained trick.

Anything that only works because one person knows the workaround is still unfinished. The knowledge sits in a head, not in the thing, and heads go on holiday, change jobs, forget. What looks like a working system is really a working person plus a fragile arrangement. The gap shows up on the day that person is not there.

Look for the step you never write down, the one you would mention if you were standing beside someone. Put it into the instructions, or better, change the work so the step is no longer needed. If neither is possible yet, at least say out loud that it exists.