invalid lot number When receiving POs using WMS

Dear Gurus,

I found errors when receiving POs on WMS.

If item lot numbers have more than 40 chars.

I found error 'invalid lot number' after type the lot confirmation field.

please check these attachments below:

1. Manually type the lot confirmation field

output :  Invalid Lor number.

2. Personalize the form, change lot number confirmation field into readonly & copy value from lot field

output : Succes

Please tell me why it can not be filled if not read only field ?

Thanks,

Wijaya