Hulao (558) — the same event in Book of Northern Qi and Book of Zhou

Book of Northern Qi: In the fourth month, Sima Xiaonan, governor of Beiyuzhou, took his city and fled to Zhou.; Book of Zhou: Sima Xiaonan, Northern…

What each source says

In the fourth month, Sima Xiaonan, governor of Beiyuzhou, took his city and fled to Zhou.

北豫州刺史司馬消難以城叛，入於周
Location: 北齊書卷4

Sima Xiaonan, Northern Qi governor of Beiyuzhou, brings his prefecture to submit; Daxi Wu and Yang Zhong go to receive him

三月甲午，齊北豫州刺史司馬消難舉州來附，遣柱國、高陽公達奚武與大將軍楊忠率眾迎之。
Location: 周書卷4 明帝2年3月