Problem:
The user is using a checkboxes custom field for users.
He then created a view of users and applied a query filter on this field, but their results were wrong.
Solution:
First of all, the checkboxes field should not save 0 when an option is not selected.
Checkboxes fields are saved as a serialized array where each selected option has a unique ID and a value. Check this screenshot https://prnt.sc/131l2xn
It turns out that the user was importing the values of the checkbox from a user-made XML file instead of a Toolset Export. This file was using unique IDs, built from the same base and an incremental suffix.
This makes the view fails, because it use SQL LIKE "%option-ID%"
