Problems have cropped up.

问题来了。

《新英汉大辞典》

Many of the problems have cropped up in my mind.

许许多多的问题一直出现在我的脑海里。

youdao

We are glad to see that the general situation in the country and in all industries has been stable. No big problems have cropped up, and this has greatly boosted our confidence.

我们高兴地看到，全国以及各行业的总的情况是稳定的，没有出现大的问题，从而大大增强了我们的信心。

youdao

You know, partial shutdowns have occurred when problems have cropped up.

NPR: Alaskans Speak Up About Oil Field Shutdown