"should be returned to the same". what can I write instead of this to avoid the passive voice error or can be written in an active voice?
If a passive sentence hides the subject, just concentrate on finding and presenting the subject, even if it isn't quite clear or doesn't quite make sense. To get there, it helps to start with the object of the sentence (easily removed if an object is unneeded - it's just hypothetical; booted at any time):
"Something "should be returned to the same" (...?)
What is the object?--It's not given. So, we'll say a VCR.
"A VCR should be returned to the same..."
So, that's the object, the verb, and a hidden subject. Maybe the subject could be Bill, or Ted, or even Bill and Ted! And after Bill & Ted return the VCR, maybe the subject becomes anyone....maybe me...? It has to be structured like that above, right? Well, no - you just defer to the generic.
"One/You should return the VCR to the same location."
If the intention was no object, not even a cool VCR; then that's okay.
"One/You(/Bill/Ted/Bill & Ted) should return to the same..."
Hopefully that helps!