After ordering a nice appetizer for $6.10 on the site :) I was able to check the datetime picker on the page.
This datetime picker is built in your_joomla/administrator/components/com_j2store/helpers/strappers.php
and from line 223 you have to change the following lines from this:
I would take a copy of the original site having issues and load it into a different a directory on the same hosting account to try and keep the test environment as close as possible to the live site having the issues by making minimal changes, just enough to avoid conflicting with the live system, i.e. different DB & domain name. I use Akeeba normally ...
You are better served to GROUP BY item then execute your qualifying id_filters, special_filters, and other_filters conditions on the aggregate data via the HAVING clause.
For your db-fiddle demo...
GROUP BY item
MAX(CASE WHEN tag IN ('Used') THEN 1 ELSE NULL END)
AND MAX(CASE WHEN tag IN ('Brake') THEN 1 ELSE ...