“That’s not true. Your plugin is breaking it. With any other it works fine.”
Unfortunately that is true, I wish it was not, but it is. If it was not, I could make a feature within the plugin to replace certain aspects of the results page, but WordPress and the templating system is not built that way. Maybe I am missunderstanding something here, but all the plugin can do with the results page is to basically ‘push’ it’s own result IDs to the main query, to replace the ones that WordPress was originally trying to query/pass to the results page.
If you think there is bug, or there is something going on, that is not supposed to – then feel free to let me know, I will do my best to correct it. In that case, please let me know the page where I should test, and every possible detail I should be aware of (what phrase should I try, what should I expect as a result etc..)
I am not saying, that the plugin is not the cause, but I need a way to test it, to see the issue, and correct it if possible, I hope you understand that.
It is also possible, that the default search results page is already a custom built one, and might require an additional argument to work – some themes have custom built search queries, which use custom forms and pass custom arguments to the results page. It is also possible, that there is a secondary search override function used by the theme – but this is not something I can tell by looking at the replaced search bar.
The filters by default work in an ‘AND’ logic
Let me re-phrase that, my mistake. It simply means, that each selected value should match – the order does not matter whatsoever.