How Can I Change Background Every Scene

Hi guys,
I have made game type puzzle like this:


But I want change background every scene and I insert background as object and set it to decoration and fixed. Each background have same size 900*1400. I also set Edit/Align scene.
However, some scene still mix backgound with previous scene. I don't know cause of problem. Because I checked each scene have distance scene is 1400 equal with size of background.
Please help me. Thanks you so much

 

The level have problem like that. When I next checkpoint

 

After Align Scene


For example, Start and Level 2, Level3. They seem be good but start level 4 they have problem

 

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