https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html#function_group-concat

In another case of the being burned due to not looking at the documentation properly and blindly copying a query,the root cause of a field issue turned out to be MySQL function GROUP_CONCATE truncating the result of the query to 1024 by default unless group_concat_max_len is set explicitly. Plus depending on the way of processing this query results in your program, it is unlikely to figure out the results were ever truncated.