I edit the IPA input for my own usage. Every other part works excellently, but when I type in the space bar, the font I use would suddenly change. Would like to find the reason.

我为了个人使用，编辑了IPA输入法。其他部分都非常完美，但当我键入空格后，我原本的字体会突然改变。这是什么原因呢？