Uploaded attachments preview are corrupted

Why are some .docx, .pptx attachments seems corrupted.
Normally upon clicking an attached “.docx” file, it is automatically downloaded.

However, at some incidents, AppSheet opens a preview but seems corrupted(see screenshot below).
Same when previewing through google drive.

Upon further checking on the Google Drive details, it was uploaded as type “text” instead of “Word”.
Any idea why it is uploaded in the wrong type?

AppSheet Preview

Google Drive Preview

Google Drive File Type(incorrect)

Expected Google Drive File Type(should be).

Thanks in advance