Hi Kurthis,
Kindly find the document attached.
This document was opening just fine using MS Word, when I opened it in syncfusion word editor and saved it, then downloaded it again and tried to open it using MS Word.
It shows the following error message:

I suspect it's related to using MS Word Shapes in the document as they're not supported with the syncfusion editor. But not 100% sure.
Thanks,
Attachment:
Test_(2)_d8f5178e.rar