BART warned riders early Friday morning about major systemwide delays due to a train that became disabled at the Lake Merritt station in Oakland. The problem occurred before 5 a.m. and BART was hoping to recover as the morning went on. About 5:30 a.m., the agency also said it was recovering from a second problem: an equipment issue that prompted 10-minute delays at the San Bruno station. Sarah Ravani is a San Francisco Chronicle staff writer.