Why are data records in database tables being erased?

Question

PHP

When running a web application created with php and MySQL.
From time to time, data records in database tables are erased. This happens randomly and frequently until I placed the web application behind the Sucuri firewall. Just recently had the same issue and I'm wondering what could be a malicious SQL injection that is causing this issue.
We use Sucuri to control code injection, but with a database, I really don't know if Sucuri can prevent that.

Answer 1

We do not use Sucuri and other third-party software to restrict access within the system.
We define areas of responsibility and correctly set the rights to access files inside the database (database user rights), and we do not observe any problems with data loss in the database (and with unauthorized changes to files).
What do we recommend to you?

Answer 2

Do you have logs?
Determine who, when, from where and with what request cleans your database and close this hole