A family of Microsoft word processing software products for creating web, email, and print documents.
Hi hitbuyi,
Thank you for the screenshot.
From the image, this does not appear to be a widespread or known Word issue. It may be related to how the mathematical character is being rendered by the font rather than a general Word equation bug.
I'm sorry that you're experiencing this problem.
In the meantime, please try using a different math font (if available in your environment) and check whether the same equation displays correctly. If the issue only occurs with a specific font, that would help narrow the cause to font rendering rather than the Word equation engine itself.
Since we've reached the limit of troubleshooting that can be performed in the Q&A forum, I recommend contacting Microsoft Support for further investigation. They can collect additional diagnostic information and determine whether this is a product issue or a font-rendering problem.