Read the updated documentation section about the @NotFound mapping: https://docs.jboss.org/hibernate/orm/5.6/userguide/html_single/Hibernate_User_Guide.html#associations-not-found

This is a bug fix, as the way this worked before was broken. NotFoundAction.IGNORE simply can't work with FetchType.LAZY, because in order to ignore a missing target row, the target row must be joined so that we can see if it exists. NotFoundAction.EXCEPTION is a way to eagerly throw an exception, but usually, when you use FetchType.LAZY with a broken FK value and without the @NotFound mapping, you will get an exception when loading that proxy on first access.

If you want broken proxies that produce an exception on first access, then simply remove the @NotFound annotation.