"This is a misunderstanding!"

Translation: 这是一个误会！

[KX3.]

这是一场误会！

[mendosi]

That was also my first impression and I came to the comments to see what others thought about this matter. CC-CEDICT lists the classifier as 個 but MoE Dict gives an example sentence with the classifier as 場 so I guess both are fine.

https://www.mdbg.net/chinese/dictionary?page=worddict&wdrst=1&wdqb=%E8%AA%A4%E6%9C%83

https://www.moedict.tw/%E8%AA%A4%E6%9C%83