Error Add Relation

Hi All,

i already using SuiteCRM versi 7.9.4.
i want add new relationship from my Custom module.
but when i add relation, popUp show error.
and when i check to Sugarcrm.log, i have this message
[FATAL] could not load RHS in Task

how i can solve this error?

please give me advice to solve this error.
thanks

air