2 sentences for 失常 (shī​cháng)

1. 自从遭遇打击后，他的行为就变得有些失常。

   zì​cóng zāo​yù dǎ​jī hòu, tā de xíng​wéi jiù biàn de yǒu​xiē shī​cháng.

   His behavior has become somewhat abnormal since he suffered the blow.

   Source: Dong Chinese Dictionary

2. 由于过度紧张，这位选手在决赛中发挥失常。

   yóu​yú guò​dù jǐn​zhāng, zhè wèi xuǎn​shǒu zài jué​sài zhōng fā​huī shī​cháng.

   Due to excessive nervousness, the contestant underperformed in the finals.

   Source: Dong Chinese Dictionary