International students getting different detection results than domestic students

i’ve been keeping informal notes for my own sanity since january and i noticed something i cant explain away easily. across my three sections this semester, international students have been flagged by our schools AI detector almost three times as often as domestic students on the same assignments, same rubric, same detector run by me personally so its not a teacher bias thing in terms of who submits to the tool. i went back and read a handful of the flagged international student essays myself and most of them read like genuine, if slightly formal, student writing to me. im not accusing the detector of being biased on purpose but the pattern is hard to ignore. has anyone else tracked this kind of thing at their school? and if the pattern holds up, what do we even do with that information, like do we stop using the detector for ESL students specifically or what.