You have mentioned COND=(0,LT) in STEP13, means if Condition code of any of the previous steps is greater than '0', step 13 won't get executed.
STEP6 is givign Condition Code '4', so giving error. You either mention the STEPNAME in your above condition code against which step u want to check as u have mentioned in STEP12 or use some other Return Code to check the Conditon.
FYI, below is the brief description of Condtion parameter.
used to conditionally execute a step
m return code to be used in comparison
0 step ran successfully
8 an error exists (probable ABEND)
12 a serious error
16 a severe error
operator type of comparison to make
GT greater than
GE greater than or equal to
LT less than
LE less than or equal to
EQ equal to
NE not equal to
stepname name of the step whose return code is to
be used in the comparison (if stepname is not
used, the comparison is made to all preceding
return codes from all the preceding steps).
ONLY the step is executed ONLY if the previous step
EVEN the step is executed EVEN if the previous step