Most of what determines whether a problem is remembered badly happens in the first reply, before anything has actually been fixed. The fix matters; it just matters later than people expect.
The first reply is doing one job only: confirming that a real person has read the message and understands what went wrong. It does not need a solution, a timeline or an explanation. Attempts to supply all three at once usually delay the reply by a day, which is the one thing that reliably makes the situation worse.
Explanations are worth giving after the problem is resolved, not during. Given early they read as excuses, however accurate they are; given late they read as candour. The words can be identical.
What almost never helps is the passive construction — an error occurred, the item was damaged — which removes the actor from the sentence at precisely the moment someone is trying to work out who is dealing with it.
Details of returns, replacements and timescales are set out in the terms published elsewhere on this site.
