Navient, the nation’s third-largest student-loan servicer, has been chastised for its customer service and is fighting lawsuits from the U.S. government, schoolteachers and multiple state attorneys general who say the Wilmington, Del.-based company routinely has mistreated customers. Noting that the company’s performance has lagged the stock market, activist hedge fund Canyon Partners last year offered to buy Navient and take it private. Navient refused, and Canyon threatened a proxy battle, building up a stake of about 10 percent of the company’s shares. Instead, the two sides agreed last month to a cease-fire and jointly nominated two new directors.