Cannot change alphabetic order

I have a dictionary project Finnish–Esperanto, i.e. the entries are in Finnish and translations in Esperanto. What I want is that Finnish entries are in the alphabtic order, which IIUC is defined by the sorting order of the vernacular writing system. If I go Tools → Configure → Set up Vernacular Writing Systems, I see that there is Finnish. It has on the tab “Sorting”, setting “Sort” as “Same as another language” and “Language” as “Invariant Language”. If I change the latter to “Finnish” and click “Save”, the sorting order does not change, even if press “Refresh” in the Lexicon Edit view or reopen the whole application. Actually my setting is not saved at all, because when I next time look at it, it is still “Invariant Language”.

While I could live with wrong order in FLEx, having an output (like an ePub dictionary) in wrong alphabetical order is a no-no.

Running FLEx 9.0.17

To precise the current order looks like to be the German one where for instance a and ä are equally valued, and which is not correct for Finnish.