We recently installed zVSE 6.1 and Sort on our test environment. During our testing phase we encountered this problem with variable length record.
// EXEC SORT,SIZE=2M
MERGE FIELDS=COPY,ORDER=1
RECORD TYPE=V,LENGTH=182
INPFIL BLKSIZE=1618
OUTFIL BLKSIZE=1618
OPTION LABEL=(S,S)
END
/*
The lengths specified for variable-length records must include the
4-byte count field.
In this case LENGTH=186