Hi,
There might be issue with the template on that page, even if the plugin is disabled the search query is not respected, it is unrelated to ajax search pro unfortunately.
This usually happens when something is set up incorrectly in the theme, perhaps the loop on the search results archive is not set to the current query or something similar to that. If you are using Elementor or similar, then check the results page template, and make sure that the module is set to use the current query as the source and not a predefined set of posts (latest or similar).