Button "Position" can't work in sm30 when use Table maintenance generator

Hello guys,

i have created a table and use 'Table Maintenance Generator' to generate the code. When i run sm30 and click the button 'Position', it can not work.

i enter '/h' to debug it and find the value'POSI' is not assigned to ok_code.

Some tables created before are OK. What's the matter with it?

Many Thanks