Something is altering $value in a way that breaks it. This is likely being caused be an acf/load_value filter or an acf/format_value filter that is running before the built the built in acf/format value filter for the repeater is running.
You need to find filters in your theme and see if one of them is causing this. Also, I noticed from your field group that you are using ACF Extented. The cause could be something in that plugin, I would try deactivating it and see if that clears up the issue.
