is vertical sync problem normal when sudden change in bright scene to dark?
 

I have a 10year old production monitor, I notice sometimes when a fast scene or a sudden change of scene from dark to bright scenes my monitors vertical hold cant hold for a millisecond. my source is coming from my non-linear editing Is this normal or there something wrong with my monitors? this only occurs when a very dark scene cuts to a bright scene viceversa.

possible that the 7.5 IRE is not set correctly.

7.5ire is not set on the video source? so theres no problem with my monitor? any of you guys experience this? I tried it on my other 2 monitors they do the same thing. all are 10 year old production monitor. but when I view it on my ordinary 5year old Televisionv (not a monitor) it doesnt.