I know now what the problem was in my case. I did what the customer service said but didn't work..tho it gave me an idea. Anyway the email from them is below,
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I replicated the issue and found your file contains layers, which is causing the text is outside the margin error.Transparencies/layers lead to conversion errors and manufacturing errors at the time of printing.To fix this issue, I recommend converting your file using the “Print to PDF” option. This will flatten any transparencies or layers present in the file. The ideal PDF format will be PDF/X and you can find more information in our Help:https://kdp.amazon.com/help/topic/G202145060For more information on transparencies, refer to our help:https://kdp.amazon.com/help/topic/G202169030#transparenciesOnce you have fixed the issue, you can re-upload your manuscript and approve the previewer.For more information on re-uploading the content file, check Help:https://kdp.amazon.com/help/topic/G202176900
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I realized that I have two images layered in the page, so I deleted one of them and I got no errors. I had few pages of errors and all of them had layered images, I have fixed all of them and now all the errors are gone.
Hope it will help!