Do not let a small mistake grow while you search for a more flattering description.

Time spent hunting for a kinder wording is time the problem has to itself. The instinct is understandable, since nobody wants to be the source of bad news about their own work, but the delay is what converts something minor into something expensive. By the time the flattering version is ready, the honest version has grown teeth.

Notice that something has gone wrong and say the plain sentence first, worrying about presentation afterward. Lead with what happened and what you are doing about it. People forgive the error far more readily than they forgive the week it spent hidden.