Page shows extra post when sticky posts are used

I use the free plugin to show 9 posts + pagination (3 articles in 3 rows). If I use 3 or more sticky / keep at the top posts, the number of articles seen on page one sometimes jumps to 10 instead of 9. So one article falls into the 4th row.

It also happens with less stickies, like 2 stickies for 6 posts (3 articles, 2 rows). Can’t find a pattern or a solution, as it sometimes just works and after writing another article it might be broken again.

Any idea what to do?