Tranquility, tranquility is for the duration of a tasbih.

Tranquility in the movements, okay, and not khushu'.

Khushu' is not a pillar, the pillar is tranquility, and tranquility as the Prophet ﷺ said: Recite what you know of the Quran, then bow until you are tranquil in your bowing, it is to remain.

In the pillar, the scholars said it is for the duration of a tasbih.

Then rise until you are tranquil standing.

Then prostrate until you are tranquil in prostration for the duration of a tasbih. As for movement, this contradicts khushu' but does not contradict tranquility.

So this lack of khushu' reduces the reward of the prayer, but it does not invalidate it.