Upgrade CrashPlan on Synology

My Crashplan installation stopped working a while ago now it’s time fix it.
Update: A few days  after I did this there was a new release available from pcloadletter at http://packages.pcloadletter.co.uk/ so I just installed it and it works perfectly. I recommend to use the packaged version instead of modifying as I did.
On my laptop, Mac OS X, I have version 4.4.1 of Crashplan and on the server it is the 4.3.0-0033 package.
The server log says:
I 09/10/15 03:37PM Upgrades available at central.crashplan.com:443
I 09/10/15 03:37PM Downloading a new version of CrashPlan.
I 09/10/15 03:58PM Download of upgrade complete - version 1430802000433.
I 09/10/15 03:58PM Installing upgrade - version 1430802000433
I 09/10/15 03:58PM Upgrade installed - version 1430802000433
I 09/10/15 03:58PM CrashPlan stopped, version 4.3.0, GUID 646867822750203914
I 10/03/15 02:13PM Synology repairing upgrade in /var/packages/CrashPlan/target/upgrade/1430802000433.1441893534258
You can view the log on the server or via the web interface.
> tail -20 /var/packages/CrashPlan/target/log/history.log.0
If I list the update directory it looks like this:
> ll /var/packages/CrashPlan/target/update
drwxr-xr-x    4 root     root          4096 Oct  3 14:53 .
drwxrwxrwx   11 root     root          4096 Oct  3 14:10 ..
drwxr-xr-x    4 root     root          4096 Oct  3 14:13 1430802000433.1441893534258
-rw-r--r--    1 root     root       9414120 Sep  3 21:55 1430802000433.jar
drwxr-xr-x    2 root     root          4096 Jul 28 15:49 UpgradeUI
-rw-r--r--    1 root     root           127 Jul 28 15:49 start.bat
-rw-r--r--    1 root     root            66 Oct  3 14:53 start.log
-rwxr-xr-x    1 root     root           247 Oct  3 14:13 start.sh
-rw-r--r--    1 root     root            92 Jul 28 15:49 startDesktop.bat
-rwxr-xr-x    1 root     root           312 Oct  3 14:13 startDesktop.sh
-rwxr-xr-x    1 root     root           135 Oct  3 14:13 startDesktopLinux.sh
-rwxr-xr-x    1 root     root           137 Oct  3 14:13 startDesktopSolaris.sh
-rwxr-xr-x    1 root     root            87 Oct  3 14:13 startFirst.sh
-rwxr-xr-x    1 root     root           211 Oct  3 14:13 startLinux.sh
-rwxr-xr-x    1 root     root           213 Oct  3 14:13 startSolaris.sh
Remove the 1430802000433.1441893534258 directory and the 1430802000433.jar file.
> rm -rf 1430802000433.1441893534258
> rm 1430802000433.1441893534258
Now try to start the application again; Action > Run
It will have the status Running but since the packaged version is wrong yo will still see Version: 4.3.0-0033 in the web ui but if you look in the log file you will se another version
I 10/03/15 03:02PM CrashPlan started, version 4.3.3, GUID 646867822750203914
I 10/03/15 03:03PM Backup scheduled to always run
And now there are a new versions to be downloaded, version 4.4.0 and 4.4.1
In my log file I see
I 10/03/15 03:03PM Upgrades available at central.crashplan.com:443
I 10/03/15 03:03PM Downloading a new version of CrashPlan.
I 10/03/15 03:04PM Download of upgrade complete - version 1435726800440.
I 10/03/15 03:04PM Download of upgrade complete - version 1435726800441.
I 10/03/15 03:04PM Installing upgrade - version 1435726800440
I 10/03/15 03:04PM Upgrade failed - version 1435726800440

You can see that Crashplan has downloaded two versions 440 and 441. It tried to upgrade to 440 but failed. Ok, what is happening here?
Crashplan is downloading the new package 1435726800440.jar and extracts it to 1435726800440.<some number>. After the file is extracted it tries to run the command ‘/bin/bash upgrade.sh‘ but of course it fails because bash isn’t installed. By default Synology uses Ash Shell on Busybox. Since BusyBox provides minimalist replacements for most of the utilities you will get the following error when trying to run the script with ash: