Unable to set some SysConfig settings to default

[schaffel]

I am in the process on updating our old OTRS 3.1 to OTRS 3.3.
I was looking through our SysConfig to document what was changed by us.
I found on the upgraded 3.3 OTRS that some settings show the icon that they were changed, but I can not reset them to default.
When i click reset the page refreshes, but there is no change in the setting. Even the the reset link is still present.

I noticed this behavior in various places.
For example I can not reset the setting CustomerFrontend::Module###CustomerFAQExplorer

Any ideas where the problem might be?
Where are the defaults defined except the xml-files the zzz*.pm configs? Is there any data about configuration in the database?

[crythias]

First, run the otrs.rebuildconfig script.

Note that items that have been configured in Config.pm can't be overwritten.

Check System Log for permission errors.

rerun the permissions change.

BTW, you did go 3.1->3.2->3.3, right?