It’s very frustrating, but I finally managed to find the solution. I tried to enter an equation when writing for a journal, and this is what I got when I inserted a fraction. The denominator and the upper part of the numerator is not displayed.
The solution seems to be with the text wrapping rather than the equation or the image itself. To solve this problem, go to “Page Layout” -> “Position” button, and choose “More layout options”, and click “Top and Bottom”. This solves my problem, phew! (prefer LaTeX very much)
UPDATE: I found another solution that allows me to use “in-line with text” wrapping, and that is simply by setting the Style of that paragraph to “Normal”. It seems that the template that I used set the style in such a way that it covers the equation.