A technician is investigating slow file transfers between a workstation and a server that traverses a single access switch. The switch port connected to the workstation shows a steadily increasing count of CRC errors, late collisions, and runts, while throughput drops sharply under load. The switch port is hardcoded to 100 Mbps full duplex, and the workstation NIC is set to auto-negotiate. What is the MOST likely cause of these symptoms?