Zero should be fixable in planning area

Hello Community,

I have following issue:

I want to set a (fixable) key figure in a planning area so that zero is fixable, too.

Therefore, I proceed as follows:

Transaction /SAPAPO/MSDP_ADMIN -> Select planning area -> Extras -> Key figure settings

Now, I want to set the flag to following key figure with according settings:

Now, when setting the 2 relevant flags (zero allowed and zero fixable):

and starting the job to change the settings in background:

.....nothing will be done.....

The job runs 0 seconds:

and when entering the change view of key figure settings again afterwards, the 2 flags have not been set:

Does anybody know what I am doing wrong or what is the issue?

Please help and reply.

Thanks and kind regards

Heinz