Java, Postgres, Redis: PostConstruct not completely working?

I would like to populate Redis from a Postgres table, and have a method that works. I would like this method to be run on application startup. However, when I try to use @PostConstruct, it seems to run the method but not successfully. I'm using R2DBC to connect with Postgres.

I've tested this by creating an endpoint that calls this method. Upon startup, I will see the "test" message printed, meaning that the method is executed. However, Redis is not populated. But then when I hit the endpoint, I see the "test" message AND Redis is populated. What the heck?

@PostConstruct
public Mono<List<Boolean>> writeRedisFromPostgres() {
    locationRepository.flushAll();
    System.out.println("test");
    return locationPostgresRepository.findAll().flatMap(
        location -> locationRepository.writeLocation(location)
    ).collectList();
}

It looks like the locationPostgresRepository.findAll() is returning empty on startup only. I put breakpoints in the method above as well as in my PostgresConfiguration class, and the configuration class is being executed first...

@Configuration
class PostgresConfig extends AbstractR2dbcConfiguration {

    @Value("${postgres.host}")
    private String host;

    @Value("${postgres.port}")
    private Integer port;

    @Value("${postgres.username}")
    private String username;

    @Value("${postgres.password}")
    private String password;

    @Value("${postgres.database}")
    private String database;

    @Override
    @Bean
    public ConnectionFactory connectionFactory() {
        return new PostgresqlConnectionFactory(
            PostgresqlConnectionConfiguration.builder()
                .host(host)
                .port(port)
                .username(username)
                .password(password)
                .database(database)
                .build()
        );
    }
}