When changing clefs, the position of - some - subsequent lines and symbols jumps with the notes; and then after another clef change it doesn't jump back to the initial position. This can cause for many objects to be wrongly placed, if the user doesn't watch out.
PS: This only happens with some lines (which usually transpose), although that isn't possible to determine which ones they are.
PSS: For lack of time I couldn't provide a detailed explanation in which conditions this happens. If necessary, I can search for concrete examples.