Problem in grid with coro column type and onEditCell event

When I use coro (combo ready only) in association with onEditCell event on grid (dhtmlxGrid v1.5 pro) causes the coro cell freese and the value can’t be changed. how to solve this problem?

Please be sure that code of onEditCell events has
return true;
at the end. Returning any other value will result in blocking of edit operation.