A slight error in thought may constitute a life-long regret.

一念之差终身之悔。

《新英汉大辞典》

Many times their immune systems are severely compromised from the cancer medications and treatment. Even a slight error or alteration of their medication could have a devastating, negative effect.

癌症病人通常是最容易受到伤害的病人之一，癌症药物和治疗经常严重危及他们的免疫系统，即使是用药过程中犯一个小错误和稍微改变用药，也可能带来灾难性的反作用。

youdao

However, a slight error with his final stone allowed Edin a double take-out opportunity, which he converted to force the British skip to take one and send the game into an extra end.

BBC: GB men's curlers out after losing to Sweden

Paul, before Denver most polls gave Barack Obama a slight edge, often within the margin of error, but an edge.

NPR: After Conventions, McCain Takes Lead In Some Polls

Some sources of potential error have been known for a long time (for example, because of slight changes in their orbits, satellites do not always take temperature measurements at precisely the same time of day).

ECONOMIST: A heated controversy | The