Magento 2.3 - Can't change any settings in backend

Question

EDIT: I noticed that I can't change any setting anymore! It just resets after save to the old value. No error message is shown.

Old Title: Theme does not change, even though database value changes If I change the theme in Content -> Design -> Configuration

Then it always changes back to the old theme even though I can see that the value is changed in the database. (Table "core_config_data" -> path: "design/theme/theme_id")

If I reload the frontend, then it still loads the old theme though.

How can I fix this bug? I already cleared the cache with

php bin/magento cache:flush

Answer 1

The problem was, that I executed php bin/magento app:config:dump which changed the files app/etc/env.php and app/etc/config.php.

I found the answer here.

You have to edit the file app/etc/config.php. Remove everything but the modules array and then save. Then run php bin/magento setup:upgrade