Error "java.sql.SQLException: Invalid utf8 character string: 'ACED00'"

[Holt31]

So I'm new using this Plug-In, when one of my Users, that had registered to the server tried to log in, then I'm getting the following exception in my BungeeCord-Serverlog:
05.04 22:16:46 [Server] SEVERE java.sql.SQLException: Invalid utf8 character string: 'ACED00' 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:965) 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3933) 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3869) 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2524) 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2675) 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2465) 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1912) 05.04 22:16:46 [Server] SEVERE at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2020) 05.04 22:16:46 [Server] SEVERE at net.leonardo_dgs.abungeeauth.database.SQLDatabase.query(Unknown Source) 05.04 22:16:46 [Server] SEVERE at net.leonardo_dgs.abungeeauth.User.comparePassword(Unknown Source) 05.04 22:16:46 [Server] SEVERE at net.leonardo_dgs.abungeeauth.cmd.player.CmdLogin.execute(Unknown Source) 05.04 22:16:46 [Server] SEVERE at net.md_5.bungee.api.plugin.PluginManager.dispatchCommand(PluginManager.java:192) 05.04 22:16:46 [Server] SEVERE at net.md_5.bungee.api.plugin.PluginManager.dispatchCommand(PluginManager.java:142) 05.04 22:16:46 [Server] SEVERE at net.md_5.bungee.connection.UpstreamBridge.handle(UpstreamBridge.java:148)

I'm using the following configuration (Renamed the type of the config from yaml to log, so I can upload it here):
config.yml

My Bungeecord-Version is:
This server is running BungeeCord version git:BungeeCord-Bootstrap:1.15-SNAPSHOT:f1c32f8:1489 by md_5

Bungeecord and Server are in offline-mode.

My Database is using the following collation: "utf8_general_ci".
The register command works like a charm. The password used is: "Jani".
The login command "/login Jani" is producing the output above.