This problem has only occurred once.

这种问题只发生过一次。

youdao

According to the information that we have at this time, the incident only occurred once.

就我们目前掌握的情况，这次事件还是一次偶发事件。

youdao

According to its risk model, one investment bank suffered a loss on several consecutive days that should only have occurred once in 14 life-spans of our universe.

按照这种理论的风险模型，一家投资银行连续几天内遭受的损失之巨大，其发生的概率为14个我们宇宙寿命的时间内才会出现一次。

youdao

The crises in various the smaller oil producing nations occurred once oil production and revenues dropped and subsidies declined.

FORBES: Saudi Regime Isn't The Culprit NYT's Friedman Claims, Says Prince Alwaleed

For most of his life, Faustino's sole human contact has occurred once every two years, when he herds his cattle to the nearest town to sell.

CNN: The loneliest cowboy in the world

That occurred, to the -- and I believe that occurred only once in February of 1997.

CNN