Event.COMPLETE and FP9

I have a client who was saying that the preloader remained on top of everything even when it hit 100%. I had not experienced this before so I asked what version of FP he had…He has FP9 . I had FP10 .

So install an archived version of FP9 and sure enough it does what he said…has anyone heard of this??? I tried this in safari and ff on a mac and both had the same result