Meta Box

https://digitaldomain.it/screenshot/Metabox-error.mp4

If it helps, I exported all post type and custom fields definitions and re-imported on a different install and everything was fine.

My test
- deactivated all custom scripts (PHP, js, css)
- disabled all add-ons
- deleted all field groups
- created a new field group and put some elements into that group (only standard values) updated/saved
- reloaded field group edit page

console

JSON Test

{
    "post_type": "meta-box",
    "post_title": "text",
    "post_date": "2023-03-19 21:24:13",
    "post_status": "publish",
    "post_content": "",
    "settings": {
        "object_type": "post",
        "post_types": [
            "post"
        ],
        "context": "normal",
        "priority": "high",
        "style": "default",
        "tab_style": "",
        "tab_default_active": "",
        "custom_table": {
            "name": ""
        },
        "class": "",
        "prefix": "",
        "text_domain": "your-text-domain",
        "function_name": "your_prefix_function_name"
    },
    "fields": {
        "text_wgxd0oufs5": {
            "_id": "text_wgxd0oufs5",
            "name": "Text",
            "id": "text_wgxd0oufs5",
            "type": "text",
            "label_description": "",
            "desc": "",
            "std": "",
            "placeholder": "",
            "size": "",
            "prepend": "",
            "append": "",
            "datalist_choices": "",
            "max_clone": "",
            "add_button": "",
            "admin_columns": {
                "position": {
                    "type": "after",
                    "column": "title"
                },
                "title": "",
                "before": "",
                "after": ""
            },
            "columns": 12,
            "tooltip": {
                "icon": "",
                "position": "top",
                "content": ""
            },
            "before": "",
            "after": "",
            "class": "",
            "sanitize_callback": "",
            "save_field": true
        },
        "text_7pk0reznyap": {
            "_id": "text_7pk0reznyap",
            "name": "Text",
            "id": "text_7pk0reznyap",
            "type": "text",
            "label_description": "",
            "desc": "",
            "std": "",
            "placeholder": "",
            "size": "",
            "prepend": "",
            "append": "",
            "datalist_choices": "",
            "max_clone": "",
            "add_button": "",
            "admin_columns": {
                "position": {
                    "type": "after",
                    "column": "title"
                },
                "title": "",
                "before": "",
                "after": ""
            },
            "columns": 12,
            "tooltip": {
                "icon": "",
                "position": "top",
                "content": ""
            },
            "before": "",
            "after": "",
            "class": "",
            "sanitize_callback": "",
            "save_field": true
        },
        "radio_y0zgtle5tco": {
            "_id": "radio_y0zgtle5tco",
            "name": "Radio",
            "id": "radio_y0zgtle5tco",
            "type": "radio",
            "label_description": "",
            "desc": "",
            "options": "",
            "std": "",
            "max_clone": "",
            "add_button": "",
            "admin_columns": {
                "position": {
                    "type": "after",
                    "column": "title"
                },
                "title": "",
                "before": "",
                "after": ""
            },
            "columns": 12,
            "tooltip": {
                "icon": "",
                "position": "top",
                "content": ""
            },
            "before": "",
            "after": "",
            "class": "",
            "sanitize_callback": "",
            "save_field": true
        }
    },
    "data": [],
    "meta_box": {
        "title": "text",
        "id": "text",
        "text_domain": "your-text-domain",
        "function_name": "your_prefix_function_name",
        "fields": [
            {
                "name": "Text",
                "id": "text_wgxd0oufs5",
                "type": "text"
            },
            {
                "name": "Text",
                "id": "text_7pk0reznyap",
                "type": "text"
            },
            {
                "name": "Radio",
                "id": "radio_y0zgtle5tco",
                "type": "radio",
                "inline": false
            }
        ]
    }
}