这一推理是不稳固的，经不起推敲。

The reasoning is ___unstable, collapsing under scrutiny.

这个地区的经济形势依然不稳定。

The economic situation in this area is still ___unstable.

这张桌子有点不稳，别把饮料放在边上。

This table is a bit ___unstable, don't put your drink near the edge.

她情绪不稳定，时而大笑时而大哭。

She is emotionally ___unstable, laughing one moment and crying the next.