I ran mysqltuner and got recommendations

OPTIMIZE TABLE b1533-UkcF.b_sec_session; -- can free 4448 MB 

But this is not correct mysql command, so may be it's better to generate this with correct quotes like

OPTIMIZE TABLE `b1533-UkcF`.b_sec_session; -- can free 4448 MB 

As I remember there was other cases with lack of quotes/backticks somewhere.