The Slotted Drive - Types of Screw Drive Styles

So, your best bet will be to use pliers and unscrew it using pliers, and tighten with pliers as well I would probably find a replacement screw

Ubervia® Cheese Head Slot Screw, Uniform Force Good Fastening Effect A2‑70 Stainless Steel Corrosion Prevention Slotted Screws for Machinery

slot machines free play Phillips head screws are designed to not be over tightened The angled slot helps push the screwdriver back out as you continue to torque

slot car racing Single-slot screws Creation in carbon steel, inox, and with galvanic treatments Production of cap screws, cap head screws, flat countersunk head both cross