Disconnect Message Received from Unknown Client

The following is a sample error log when disconnect message is received from an unknown client.

[radius-ep-n0-0]  
[radius-ep-n0-0] 2020/11/25 10:30:02.960 radius-ep [INFO] [processor.go:157] [Radius.smf.Ipc] Process continue - 2003 
[radius-ep-n0-0] 2020/11/25 10:30:02.960 radius-ep [DEBUG] [coa.go:23] [Radius.smf.AAA] [] [] [11] Coa/Disconnect Req received from udp proxy 
[radius-ep-n0-0] 2020/11/25 10:30:02.960 radius-ep [DEBUG] [coa.go:43] [Radius.smf.AAA] [] [] [11] SrcIp: 198.18.1.20 SrcPort: 3799 DestIp: 198.18.1.4 DestPort: 3799 
[radius-ep-n0-0] 2020/11/25 10:30:02.960 radius-ep [ERROR] [coa.go:253] [Radius.smf.Ipc] Bng Coa/Disconnect req failed - Invalid Coa Client 198.18.1.20 
[radius-ep-n0-0] 2020/11/25 10:30:02.960 radius-ep [ERROR] [coa.go:48] [Radius.smf.AAA] [] [] [11] Unable to process Coa/Disconnect request - Error during init of Radius Message Invalid Coa Client 198.18.1.20 
[radius-ep-n0-0] 2020/11/25 10:30:02.960 radius-ep [DEBUG] [MasterBlueprint.go:345] [infra.transaction.core] Last stage ( init_done ) -> Next stage ( finished ) 
[radius-ep-n0-0] ************* TRANSACTION: 00011 ************* 
[radius-ep-n0-0] TRANSACTION SUCCESS: 
[radius-ep-n0-0]     Txn Type             : RadiusUdpProxyCoaMsg(2003) 
[radius-ep-n0-0]     Priority             : 1 
[radius-ep-n0-0]     Session State        : No_Session 
[radius-ep-n0-0] LOG MESSAGES: 
[radius-ep-n0-0]     2020/11/25 10:30:02.960 [TRACE] [infra.message_log.core] >>>>>>>> 
[radius-ep-n0-0]  
[radius-ep-n0-0]     2020/11/25 10:30:02.960 [DEBUG] [Radius.smf.AAA] Coa/Disconnect Req received from udp proxy 
[radius-ep-n0-0]     2020/11/25 10:30:02.960 [DEBUG] [Radius.smf.AAA] SrcIp: 198.18.1.20 SrcPort: 3799 DestIp: 198.18.1.4 DestPort: 3799 
[radius-ep-n0-0]     2020/11/25 10:30:02.960 [ERROR] [Radius.smf.AAA] Unable to process Coa/Disconnect request - Error during init of Radius Message Invalid Coa Client 198.18.1.20 
[radius-ep-n0-0]     2020/11/25 10:30:02.960 [TRACE] [infra.message_log.core] <<<<<<<< 
[radius-ep-n0-0]  
[radius-ep-n0-0] *********************************************** 
[radius-ep-n0-0]