Encountered 'DB errors: duplicates' when searching for ojs categories in the search engines

Hi @Kantapong_Phumyoo

This thread is quite similar to your question and an user shared his solution, please take a look:

But, even it works to either, I suggest you to update your OJS.
Version 2.3.6 is a kind of old code and newest versions has fixes to bugs that you may encounter in your current one.

Regards,
Israel Cefrin
Public Knowledge Project Team