IN the code, acqui/edi_ean.pl:

 41 if ( @eans == 1 ) {
 42     my $ean = $eans[0]->ean;
 43     print $query->redirect(
 44         "/cgi-bin/koha/acqui/basket.pl?basketno=$basketno&op=cud-ediorder&ean=$ean"
 45     );
 46 }


Redirect doesn't send the post variables, so the redirect fails with:
Programming error - op 'cud-ediorder' must not start with 'cud-' for GET http://localhost:8081/intranet/acqui/basket.pl?basketno=76&op=cud-ediorder&ean=REFW (referer: http://localhost:8081/cgi-bin/koha/acqui/basket.pl)


Work around, define a second EAN :-)