Product Configuration Rules - "Set characteristic value for configurable product"

Hi there, I'm working on a CPQ project. Everything goes well. Now additionally want to use the "Product Configuration Rules" (In Backoffice go to SAP Integration >> SAP Product Configuration >> Product Configuration Rules).

The most rules work very well and show the expected behaviour. So, it's easily possible to show messages or hide assignable values etc.

Except "Set characteristic value for configurable product". This one should set the default value for an characteristic. But in my test cases this never works. Does anybody have seen this working or know a little trick to get this working?

Btw: I'm on version 1808.

Kind regards, Ben