Sometimes Z order of several overlapping shapes might be lost when the document is opened and saved with Aspose.Word.
For example, you had a textbox to create a black background and two other textboxes on top of it with some text. When passed through Aspose.Word, the document might come out with the black background textbox on top of the other two textboxes.
We cannot fix this at the moment, but you can use a workaround:
Select the offending shape in MS Word, right click on it and choose Order/Send Behind Text.