Strange MySQL behavior : Access denied for user '3306'@'localhost'

[t.heroult]

Info
Zabbix server 5.4 (Debian 10)
host :
- windows 2016 std
- MySQL 5.7
- Zabbix agent 2
- Template : MySql by Zabbix agent

Hi folks !
I'm rather new to zabbix. I discovered it few weeks ago and I'm currently setting it in our information service...

[ucs75]

Recenly upgraded to 2.0.2 server from 1.8.

If I update the zabbix_agentd to version 2.0.2, my external checks stop working. I've also tried using the pre-compiled 2.0 agent from the download page. If I use v1.8 zabbix_agentd, it works fine.

Operating System info:
...