@dandv
probably there is a bug in the code.
while it is mentioned in the documentation that value can be number, in fact number value for multicombo is not accepted.
try to set either string value "1" or array [1]
Yep, this is a bug, thank you for the report! We’ve taken a note of it, and it should be fixed in the nearest future. For now though, please used strings or arrays instead.