Record duplication didn't copy values

I’ve a form with master screen section and several tabs with detail screen sections. When I duplicate a master record, several values in details are copied and several details are not copied. All entity fields in details tabs have set OnCopyAction to Copy. Is there anything else to be set, so the values detail screens are copied on duplication action?

Maybe ‘IsWriteOnly’ in a datastructure field. This feature is frequently used for blob columns - see Using BLOB column

So maybe you have it there and not the BlobLookup specified?

Otherwise I don’t know. Please tell if it helped