hit-and-miss

adj. /ˌhɪt.ənˈmɪs/

If something is hit-and-miss, you cannot depend on it to be of good quality, on time, accurate, etc.

没准的，碰运气的

The trains are often late, so getting to work on time is a fairly hit-and-miss affair.

火车经常晚点，所以准时上班在很大程度上是件碰运气的事。

I'm really sorry, my internet connection has been a bit hitand miss today.

对不起，我的互联网连接今天有点时好时坏。