It’s possible that if your search plugin is building queries that reference the events custom post type (including if it searches all post types) – and performs something called a join operation against the postmeta table in the database – this will conflict with our own query logic which also performs a join operation on that same table, whenever it detects that a database query relates to events.
I’m not familiar with Advance WP Query Search Filter, but one way to test this theory out – if it has a suitable option to achieve this – would be to stop it from searching for event post types / restrict it temporarily so it only searches regular posts and pages.
If it functions correctly in those conditions, this could indeed be the problem.