First of all, in Word tables, it is common that cells (whether in the middle of the table or near the table border) are misaligned. As shown below, the main reason should be that the cell was selected before, and then its row width was artificially changed.

Secondly, the solution is to click the left mouse button on the cell three times to select it, and then hold down the left mouse button and drag the border line to align it with the upper and lower border lines.