Hello, we use this plugin a lot in Orange IaaS to change the Freestyles Shells easily. The issue start when we use "Execute shell slicer" option.

First of all we use a Shell Terminal (in Build Task)  with Advanced option enabled "Mark as unstable with a return value", to return a Unstable when return =100.

The code associate in XML is  :

<unstableReturn>100</unstableReturn> 

If we modify some shell using "Execute shell slicer" option, this modification DELETE the Advanced code.
I think that it can be interesting to modify the Advanced part from this plugin or at least dont delete it.

The way to test this:
1) Create a Freestyle Job (i.e: "MY_JOB")

2) Add a Shell Task in Build Task

3) Select the Advanced Option and write "100"

4) Print the XML (cat $ADDRESS/config.xml)

5) Modify "MY_JOB" with  ConfigurationSlicing Plugin

4) Print the XML  again (cat $ADDRESS/config.xml)