Extra levels being created accidentally

[CG_AUS]

Hi there,
I keep finding more levels in our model - they overlap existing levels, appearing in the sections and elevations. Our building has 13 levels, but now I find levels 36-40 (all overlapping at the same RL as level 2) (it's been happening for a while now, and I keep deleting them).
I don't know how, but I'm the one doing it.
Is there a way to duplicate a level while in a plan view? That's where I spend the vast majority of my time.
Thanks

[Steve_Stafford]

Do you copy things from floor to floor while in a section or elevation view? If so, do you use a crossing window to select?

[CG_AUS]

Very rarely. If it happened while in section / elevation it would make more sense!
I do copy things from one level to another in plan view fairly often, but if I ever use a crossing window I'll filter the objects to make sure I've only got the ones I want. I just didn't think there was any way to select a level line while in plan!
Could duplicating a plan view create another level??