LinuxQuestions.org - Why is sort -k not working all the time?

I have a script that puts a list of files in two separate arrays:

First, I get a file list from a ZIP file and fill `FIRST_Array()` with it. Second, I get a file list from a control file within a ZIP file and fill `SECOND_Array()` with it

Code:

                while read length date time filename 

                do

                        FIRST_Array+=( "$filename" )

                        echo "$filename" >> FIRST.report.out

                done < <(/usr/bin/unzip -qql AAA.ZIP |sort -k12 -t~)

Third, I compare both array like so:

Code:

diff -q <(printf "%s\n" "${FIRST_Array[@]}") <(printf "%s\n" "${SECOND_Array[@]}") |wc -l

I can tell that `Diff` fails because I output each array to files: `FIRST.report.out` and `SECOND.report.out` are simply not sorted properly.

1) FIRST.report.out (what's inside the ZIP file)

Code:

JGS-Memphis~AT1~Pre-Test~X-BanhT~JGMDTV387~6~P~1100~HR24-500~033072053326~20120808~240914.XML

JGS-Memphis~PRE~DTV_PREP~X-GuinE~JGMDTV069~6~P~1100~H24-700~033081107519~20120808~240914.XML

JGS-Memphis~PRE~DTV_PREP~X-MooreBe~JGM98745~40~P~1100~H21-200~029264526103~20120808~240914.XML

JGS-Memphis~FUN~Pre-Test~X-RossA~jgmdtv168~2~P~1100~H21-200~029415655926~20120808~240914.XML

2) SECOND.report.out (what's inside the ZIP's control file)

Code:

JGS-Memphis~AT1~Pre-Test~X-BanhT~JGMDTV387~6~P~1100~HR24-500~033072053326~20120808~240914.XML

JGS-Memphis~FUN~Pre-Test~X-RossA~jgmdtv168~2~P~1100~H21-200~029415655926~20120808~240914.XML

JGS-Memphis~PRE~DTV_PREP~X-GuinE~JGMDTV069~6~P~1100~H24-700~033081107519~20120808~240914.XML

JGS-Memphis~PRE~DTV_PREP~X-MooreBe~JGM98745~40~P~1100~H21-200~029264526103~20120808~240914.XML

Using sort -k12 -t~ made sense since ~ is the delimiter for the file's date field ("20120808" : 12th position). But it is not working consistently.

The sort is worse when my script processes bigger ZIP files. Why is sort -k not working all the time? How can I sort both arrays?