There is a problem with Gutenberg 15.2.0.
After the latest Gutenberg update, when you set the Archive Excerpt to “0” in the customise>layout>blog section, this command is ignored.
I have rolled the plugin back to 15.1.1 and this error has disappeared.
Will there be an update that will fix this issue?
The WP default editor is Gutenberg now, so technically you do NOT need to install this plugin, only if you want to test the newest feature of Gutenberg, but meanwhile, the plugin is a beta version plugin for testing purposes, you will have to face the unstableness and bugs.
So it’s no point for us to fix the issue at this stage, but we will keep this in mind 🙂