Hey Michael,
To your question:
Did that happen after a theme update? Because if not, the issue is surely coming from other factors like a 3rd party plugin or a custom function.
You also said:
I believe you mean Theme Options > Blog > Excerpt Length. If you’re sure you’re using the WordPress’ Customizer that could also be coming from a 3rd party plugin or some custom code because our themes don’t use the Customizer.
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With that said, please do the following troubleshooting steps to determine if that is the case.
- TESTING FOR PLUGIN CONFLICT
- CHILD THEME
If you’re also using the Content Builder for your Posts, that could also be a possible reason why you have varied excerpt lengths. That is because the Excerpt could not read certain shortcodes and the Content Builder outputs shortcodes in the WordPress Content area.
Please create a Manual Excerpt for each of your posts. If you’re not aware of Manual Excerpts, please learn here https://kinsta.com/knowledgebase/wordpress-excerpt/
Hope that helps.