SDL Trados 2015: Excel text boxes not getting exported

I am working on an English translation of a Japanese system spec document created in Excel. It uses a lot of text boxes and drawing shapes with text inside. The text seems to have been successfully read into Trados when creating the project. However, when I export (Shift-F12) the file back to Excel, many of the text boxes are empty and missing translations. Has anyone run into this before and have any advice on how to get the text to export correctly? Thanks in advance.

System info:
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Trados Studio 2015 Freelance SR3 12.3.5281.10
Original source Excel file is *xlsx
MS Office 365 Excel v1712 (for viewing)
Windows 10