Search Results In Admin Are Terrible

The search on the front end works pretty good, but the admin side is really bad. Sure, I can do an advanced search and it provides acceptable results, but as it is now I get thousands of results that have none of the search terms I enter. What could be causing this? Is there a way to fix it so it works like it used to in earlier versions? I am running 4.2.1

It does work fine if I enter a specific sku number. But product name search is abysmal. I notice that most of the results contain a certain line of products of which we have thousands. I know it sounds weird, but could the sku prefix somehow be damaged or corrupted?

For example, I search “rainbow fish” and get around 1500 results, only 3 of which contain the words rainbow and fish. It's bizarre