Our agent just solved some ticket which does not need any reply. But his ticket comes back into open ticket even customer did not make any reply or any response. Is there any similar issues or when it can happen? It happens only one of our agent. We have tried catche clear and reset password, logged out. 
Solved ticket becomes open again even customer did not reply
Khulan Tuyaatungalag - per checking on the snippet of ticket events you sent looks like someone changed the ticket status from Solved to Open.
Since you have access to the ticket event you will be able to identify if who changed the ticket status in here.
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