Quite often you can find a pair of Chinese characters that complement one another, 机器 is one of these. Sometimes you can even switch them around. In this case you can’t. For some reason you can’t use 器机.
A 器 is a 机 and 机 is a 器 and in a way they are both 机器。That is probably why the question was asked what and if there is a difference between 机 and 器。
Oh 机器 by the way is a machine like 机器人 is a robot 人 is human. A robot is made up of many parts just like a human is made of many 器官 (organs). Each organ is a part or a device. So we see here that 机 is made up of 器s which could also be a 机 made of other 器。
In Chinese, what’s the difference between 器 and 机? 器 is a device 机 is a machine so one is bigger and more complex than the other.
机ji¹ is 機 and 幾乎 is not quite (almost) and is composed of 丝 and 戌 and has the idea of being alert, on the look out, a sentry.
器 in a way is also a sentry but instead of a soldier it is a 犬，a hound (dog), a noisy one with 㗊 four 口。
Originally picture of a dog with 㗊 (ji², noisy, 口品a device) must have been replaced, too many false alarms.
That was more than 5000 years ago. Now a single “i” is enough but it is artificial. It is not noisy, is intelligent but it could still give us false information.