Hi Wenlong,
Please check whether the agent used to monitor MySQL database is compatible with OS and DB versions or not by referring to Data Security Coverage Tool and Agent Release Notes. Secondly, did you notice any such type of gibberish data in DB user column of the audit policies?
Although we noticed such garbled DB users (but not so long like you showed), this issue was resolved after the agent upgradation.

Regards,
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SBISOC 4430
Manager
Mumbai
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