When you set the "Configuration form setting" to "hidden" in your page display, the default value of the field are not visible anymore when you want to edit your defaults (So it will be updated on every node!)
So, you need to set the Configuration form settings to "Full", otherwise the settings are not available for your block.
Make the default settings available when settings the Configuration form to "Hidden" on the form display so editors can't change any settings.
Fix this bug and write a patch
Active
1.0
User interface
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Confirming this issue still seems to exist.
Another logical issue is, that if a block has required settings and the form is hidden, these values are never set, which may lead to other errors. Perhaps the hiding-logic at all should be overthought?