Docker reads from the database but does not write to the database, what's wrong?

Question

Database administration

Raised docker, one container with a database, two nginx containers with two sites, two php-fpm containers for each site, respectively. Regarding connections, the settings are identical. With one site everything is fine, the problem is in the second site. No data is written to the database. The site works, connects to the database, reads, but when creating material, it freezes tightly and does not record.
I don't see any errors or anything. The user's privileges are already full, everything is written from the connected phpmyadmin, the problem occurs precisely with writing to the database from the site.
Are there any assumptions?