unreliable

The internet connection in this rural area is very unreliable, especially during stormy weather.

(Chinese) 这个农村地区的网络连接非常不可靠，尤其是在暴风雨天气。

He is an unreliable witness because his account of the events changed several times during the interview.

(Chinese) 他是一个不可靠的证人，因为他在采访中对事件的陈述变了好几次。