Running job YDUPAPPOBJ gets
10000 - CHKOBJ OBJ(TEST_DUP/'Y2I$DSP') OBJTYPE('*FILE') AUT(*USE) Value 'Y2I$DSP ' for parameter OBJ not a valid name.
This happens if the JOB's CCSID is not 65535
The object lists used are members of Y1USROBJ in Y1SY, these are shipped with a CCSID 65535.
A UK standard is 285 so Y2I$DSP became Y2I DSP (that's a GB pound sign) so you need to run YDUPAPPOBJ in batch with CCSID(65535) or interactively after a CHGJOB CCSID(65535).