Hi Aravind,
Was the switch for ERP client maintenance switched on? I assume so since your ECC is connecting to a MDG hub.
According to a response from an OSS I raised, this switch functionality causes an event to be registered and activated in table CRMC_BUT_CALL_FU which triggers a data outbound. This outbound may be responsible for the automatic replication.
Software switches cannot be turned off, however removing the "is active" flag for module MDG_BS_ECC_BP_OUTBOUND (event BPOUT, object BUPA) in table CRMC_BUT_CALL_FU may fix your automatic replication issue. It was mentioned that turning this active switch off could potentially cause other issues in the hub system.
Hope this helps.
Regards,