You should try tween platform and action to change camera pos
Cause behaviors can run before events and that can cause jitter
Where via events you can manually change position of events
So you can put camera change above event to move platform
Or put camera change blow move platform
In my eyes it is same issue as when you change text position and below it you change text itself and you will also get jittering
Where if you put change text above change text position
It will be smooth
And you can see that kind of issue here
Top gif in my post is when text change is below position change of text
And it jitters
And that day i discovered that if you 1st put text change then below it change text positon
It will not jitter or to be precise flicker