Is it not sufficient to have like 0,2 mm difference between the tab and the margin? I am thinking this has to do with what units Scribus uses internally and a rounding error causing it to think the tab is outside the margin or something like that?
I don't remember what units Scribus uses internally, but I think it is not mm but rather some fraction of points.
I'd question ClamWin's false positives, but also check for ClamWin updates.. last release of the program in 2021 from what I see on their website, even if they are getting ClamAV definition updates? We'll still double check further.