Host 'Hostname' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts - mysql

Question

What a strange problem!
I have the same applications running in different mysql(dev and test environment)
both 2 mysql are totally the same.
but today in dev environment, I came up with an error like this(which is never happened before):
Host 'Hostname' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts
I also find the solution to this problem, like below
here is the solution of same question but not solved
there are 24 connections in the connection pool of my applications, none of them will fail and there are also no failures at all.
Using show variables like "%max_connect%" I can see max_connect_errors are 100.
My application runs in the same ip as my navicat.
By show processlist I can see there are no other connections except navicat connection before application start. And then I tried to start my application, the problem occured and I cannot even start up my application!
after flush hosts, all the applications will be run in normal without any problem, but when I tried to restart them, the problem shows again.
I don't know what's going on!
I have 4 applications using DB, and the mysql configuration is showing below:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://${my-config.mysql.host}:${my-config.mysql.port}/${my-config.mysql.db-name}?characterEncoding=utf-8&serverTimezone=Asia/Shanghai&rewriteBatchedStatements=true&allowMultiQueries=true
username: ${my-config.mysql.username}
password: ${my-config.mysql.password}
validation-query: SELECT 1
test-on-borrow: true
test-while-idle: true
time-between-eviction-runs-millis: 10000
hikari:
minimum-idle: 1
maximum-pool-size: 10
you can see that: even all the applications use connections in the maximum pool size, ther should be only 40 connections, and also even all of them failed there are only 40 failures.
So far I have noticed that using show processinglist after flush hosts there are always 1 or 2 unauthorized connections like this:
maybe this is why my application will always down after restarting.
But I notice that that unauthorized connection is from my computer and I did not run any other applications...
Another problem is that, when the problem occurs, it shows
Host '192.168.18.19' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'"
but all the other existing connections using the same IP will not receive such report, they works well and can reach to mysql!
you can see that my gateway application was toasted because of the problem.
but my message center application using the same IP can get infomation from mysql(only if it can get rows from mysql, it print those words like 配置已更新).
If mysql blocked my IP, why other applications using the same IP will not be blocked?
Am I hacked?