hashcat unexpected output from "s" Rule

[ntk]

use hashcat-cli 0.39

command:
./hashcat-cli32.bin -r /home/k/ohc/rules/replace.rule /home/k/ohc/exam.hash --stdout /home/k/dict/test /dev/null /dev/null > /home/k/dict/analyse

test dict:
ABABABAB
ABABABAC
ABABABAD
ABABABAE
AHRQUBPW
AHRQUBPX
AHRQUBPY
AHRQUBPZ
AHRQUBQA
AHRQUBQB
AHRQUBQC

test rule:
sAB

output:
BBBBBBBB
BBBBBBBC
BBBBBBBD
BBBBBBBE
BHRQUBPW
BHRQUBPX
BHRQUBPY
BHRQUBPZ
BHRQUBQB
BHRQUBQB
BHRQUBQC


if content of test rule is sABsBC, then output on the same test dict is:
CCCCCCCC
CCCCCCCC
CCCCCCCD
CCCCCCCE
CHRQUCPW
CHRQUCPX
CHRQUCPY
CHRQUCPZ
CHRQUCQC
CHRQUCQC
CHRQUCQC

I can not make any sense of it? Strange.