What is the reason for slow Update on large volumes in CRUD Symfony2 (sonata-admin-bundle)?

Question

symfony

Good afternoon. The crux of the matter is as follows. The site is powered by Symfony2, sonata-admin-bundle admin. There are two tables connected by a one-to-many relationship. The parent table is placed in the directory, the child table is controlled by CRUD. When creating a record, as well as changing an existing one, with small data sizes in a form field with a visual editor, saving is relatively normal (there are no error messages in the debugger and there are no warnings), but you only need to make a change to the record, where the amount of data is 5- 6 pagedowns, so the response is noticeably increased and the save is delayed for a long time (more than 15 seconds). Errors are also not observed. Tell me what could be the reason? How to build the work of the form so that with large volumes everything is saved quickly enough?