If by section lines you reffer to the cut symbol position (the arrow cut symbol with the name of it attached), then those symbols should not move around during update, and keep their position (as long as their new position is on the same line as the cut direction).
If you reffer to the manual dimensions : then those normally do not move either. But to further investigation your situation, we'll need the model and the drawing which contains those dimension lines that change position. Also mention the Advance Steel version used.
As a workaround you can try to set the following default on Off before updating the drawings : Erase incorrect manual dimension points on update, from GAM / Defaults / Drawing - Dimensioning / General