Error updating sessions table

DEBUG MODE

SQL Error : 1062 Duplicate entry 'viewtopic.php?download=39439&f=68&t=3228&_f_=68x&_t_=3228x' for key 'session_page'

UPDATE phpbb_sessions SET session_time = 1788987883, session_start = 1788987883, session_page = 'viewtopic.php?download=39439&f=68&t=3228&_f_=68x&_t_=3228x' WHERE session_id = 'bee14f2ca7d02822b0451f25a936a304'

Line : 556
File : sessions.php