What is use of "Active Fix" function in status bar during Post analysis?

You can freeze the elements which are activated using the "Active Fix" at the bottom right of the window:

When you activate this function, it will lock in the elements which are currently activated and activate only those when you change stages. Note that it will always re-activate to the elements which were active when you switched on the Active Fix function. If in one of the stages you activate/deactivate some elements, if you then change the stage it will revert to the original list of activated elements. If you want to update the list, simply switch OFF and ON the function to lock in the new elements active on screen.