It is indeed global objects that is causing such a problem.
What I would do (IF and only IF you need them global) is check the attribute "Destroy on Start", and create spawn sprites that create said objects where you want them on the loading of the layout (think of Platform School, and the way that the enemies are handled in a similar way).
What I would actually do though:
Create an Include Sheet for the objects you want to continually use, then just manually copy and paste them from layout to layout.
(to add an include sheet, first right-click on the event sheets folder in the Projects Tab, and add a new one. Then, in the event sheet editor, right-click on the event sheet editor, to add one)