Search by SKU in Magento not working properly

Over 3000 of our SKUs contain special characters such as “-“, “/”, “&”. The problem is when we try to search regular SKU (e.g. ABC123) on the front end it returns the correct result; however when we try to search the SKU having special characters (e.g. ABC-123), it returns multiple results, and sometimes the original SKU doesn’t even appear on first 5 pages. How can we resolve this issue?

Thank you.