The office explaination is this.
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%IP-3-TCP_BADCKSUM:TCP bad checksum
Explanation: This message indicates that the system has received a TCP packet with a bad checksum from another device on the administrative VLAN. The packet will be dicarded.
Recommended Action: No action is necessary. This message is provided for information only.
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The "administrative VLAN" here refers to the vlan switch's sc0 interface belongs to. The best way is to sniffer that vlan. It's almost certain that there's a host box in this vlan is sending bad traffic.
