Default country can be set but cannot be saved

After migration from Joomla 3 to Joomla 4 also JEM has been moved as described in the documentation.
All former data seems to be available.
But within the JEM settings the default country "Austria" can be set but will not be saved.
When opening the screen again the setting is not stored.
An error occurs during saving.
Also when creating a new venue the default country is not set and two error lines are shown on screen.
See also attached screenshots.
Kind regards
Thomas

Hello Wolfgang,
first of all: thank you for your help and fast response (in the currently opened other issues)! This is really great.

One thing that I have seen in the code of class "defaultCountry". But in database the initial value was "DEFAULTCountry". So I've just change the value in the database to the lowercase beginning one and this seems now to work.

Maybe this is a common bug. If not, this issue can be closed.
Best regards
Thomas