in 921, that field has definition of:
0052=AN,1,3
which is correct for 001 & 1
But for newer version, for example, 99B, it has a CODES restriction of:
0052=1,2,88,89,90,D,S
which 1 is valid, but 001 is not
My guess is that you are validation against a newer version of schema in your 9.6 installation.
HTH,
#Integration-Server-and-ESB#webMethods#edi