Hi,
I see you are trying to combine an external filter with the search, which is usually not a good idea. Search plugins try to override the results by replacing them with their own, filters (or filter plugin) do the same thing – so either one or the other gets ignored at the end and either the search or the filter applies but not both.
It is not exclusive to Ajax Search Pro, basically it happens with any combination – unless they are coded specifically to be compatible (which almost never happens). For that reason we added an option to turn OFF the override so filters still can be utilized with the default searches.