Why is the data from the repeater type field no longer displayed?

Question

OctoberCMS

Help solve the problem!
Created in October CMS using plugin Builder entity Article (Article) - table and model. alex_articles_ table and Article model. In the table, I created the product field of type Text.
In the Article model, I specified the repeater type for the product (List of goods) field, that is, it will store a list of elements where each element (product) will have the following properties: product_element - description, product_name - product name, product_yotube - youtube video embed code. Specified in the model that the product will be jsonable to store complex data.
Product field structure (List of products)

product:
        label: 'Список товаров'
        prompt: 'Add new item'
        span: full
        type: repeater
        form:
            fields:
                product_element:
                    label: Товар
                    size: large
                    span: full
                    type: richeditor
                product_name:
                    label: 'Название товара'
                    span: auto
                    type: text
                product_yotube:
                    label: 'Ролик о товаре'
                    size: large
                    language: php
                    span: auto
                    type: codeeditor

The Product property is the text area of ​​the richeditor. This is how the form with the completed article looks like, there is an article and in the multiple property List of goods (product) another list of goods is indicated.

But there was a problem when there are a lot of products, all these products cease to be displayed in the admin panel, they disappear!
I thought that the problem is that the product field in the mysql database is overflowing, since each product has a detailed description sometimes for several pages and there can be 10-15 such products. Then I changed the type of the product field in phpMyAdmin from the text property to longtext. The problem remains, although now I can already save more products, but anyway, when there are more than 10 products, if each of them has a large description, then sometimes they all disappear.
I can not understand what is the problem at the mysql level in the restriction of the product field or at the model level in the structure of the multiple property List of goods?