あやこ歯科医院ブログです。

Disable all plugins except for category order to see if some other plugin is causing the problem. If the problem goes away, re-enable each plugin until you find the incompatible one.
Try switching to a different theme, like the WordPress default theme.

Once you have tried the above steps, email david@coppit.org with the results of these debugging steps. Also include the following information:

Original HTML:
<li class="cat-item cat-item-5"><a href="https://www.ayakoshika.net/blog/category/%e3%81%8a%e5%8b%89%e5%bc%b7" >お勉強</a>
</li>
<li class="cat-item cat-item-1"><a href="https://www.ayakoshika.net/blog/category/%e3%82%a4%e3%83%b3%e3%83%95%e3%82%a9%e3%83%a1%e3%83%bc%e3%82%b7%e3%83%a7%e3%83%b3" >インフォメーション</a>
</li>

Processed HTML:
<li class="cat-item cat-item-5"><a href="https://www.ayakoshika.net/blog/category/%e3%81%8a%e5%8b%89%e5%bc%b7" >お勉強</a>
</li>
<li class="cat-item cat-item-1"><a href="https://www.ayakoshika.net/blog/category/%e3%82%a4%e3%83%b3%e3%83%95%e3%82%a9%e3%83%a1%e3%83%bc%e3%82%b7%e3%83%a7%e3%83%b3" >インフォメーション</a>
</li>

Category pattern:
/http\:\/\/www\.ayakoshika\.net\/blog.*?\/category\/(?:[^\/"]+\/)*([^\/"]+)/

Items:
Array
(
[0] => <li class="cat-item cat-item-5"><a href="https://www.ayakoshika.net/blog/category/%e3%81%8a%e5%8b%89%e5%bc%b7" >お勉強</a> </li>
[1] => <li class="cat-item cat-item-1"><a href="https://www.ayakoshika.net/blog/category/%e3%82%a4%e3%83%b3%e3%83%95%e3%82%a9%e3%83%a1%e3%83%bc%e3%82%b7%e3%83%a7%e3%83%b3" >インフォメーション</a> </li>
)

お勉強

インフォメーション