We were now able to reproduce the behavior of the API. Earlier, we assigned the value to Page CropBox by following and the resultant URX was fine:
document.Pages.CropBox = document.Pages.CalculateContentBBox();
However, while testing using the below code snippet, we were able to notice the different values as result.
Aspose.Pdf.Document document = new Aspose.Pdf.Document(dataDir + "input.pdf");
var curx = document.Pages.CalculateContentBBox().URX;
var rurx = document.Pages.Rect.URX;
Therefore, we have logged an investigation ticket as PDFNET-49468 in our issue tracking system. We will further look into its details and let you know as soon as the ticket is resolved. Please be patient and spare us some time.
We are sorry for the inconvenience.