einwandfrei
flawless
Without any defects, errors, or problems; in perfect condition.
Das Gerät funktioniert einwandfrei.
The device works flawlessly.

flawless
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flawless
Without any defects, errors, or problems; in perfect condition.
Das Gerät funktioniert einwandfrei.
The device works flawlessly.

The word is made up of 'Einwand' (objection, point of criticism) and 'frei' (free). Something that is 'einwandfrei' (flawless) is therefore literally 'free of objections'.
Die Qualität der gelieferten Ware war einwandfrei.
The quality of the delivered goods was flawless.
'Einwandfrei' (flawlessly) is very often used as an adverb to describe that a process or function runs without problems. It then usually stands at the end of the sentence or directly after the verb.
Der Drucker funktioniert seit der Reparatur wieder einwandfrei.
The printer has been working flawlessly again since the repair.
In the meaning 'fehlerfrei' (error-free), 'einwandfrei' (flawless) often refers to the condition or function of devices, machines, or products. Typical nouns are 'Zustand' (condition), 'Funktion' (function), or 'Qualität' (quality).
Das Auto ist in einem einwandfreien technischen Zustand.
The car is in flawless technical condition.
When referring to character or behavior, 'einwandfrei' (impeccable) is used to express that a person or their actions cannot be criticized morally. Typical nouns are 'Verhalten' (behavior), 'Charakter' (character), or 'Ruf' (reputation).
Der Politiker hat einen einwandfreien Ruf.
The politician has an impeccable reputation.
order
'in Ordnung' and 'einwandfrei' can both say that something works or has no obvious defect. 'in Ordnung' is more neutral and often simply means: it is okay or acceptable. 'einwandfrei' is stronger and says: there are no defects or problems. That is why 'einwandfrei' sounds more precise when giving a positive evaluation of a device, a piece of work, or a condition. 'in Ordnung' is enough when something is only good enough or works normally.

Der neue Drucker funktioniert einwandfrei.
The new printer works flawlessly.
Das Fahrrad ist in Ordnung, aber die Klingel ist etwas leise.
The bicycle is okay, but the bell is a bit quiet.