STP Etherchannel Misconfig Guard is a prevention mechanism implemented on switches to check the MAC Address of BPDUs transmitted across an etherchannel bundle. It assumes that since these ports are bundled together BPDUs should be originating from the same source MAC address.
If BPDUs sourced from different MACs are received on a port channel interface it is an indication that the adjacent switch is treating the ports included in the bundle as separate independent interfaces instead of a port channel. As a result, STP Etherchannel Misconfig will place the ports of the bundle into an err-disabled.
STP Etherchannel Misconfig is active by default and can be deactivated using the no spanning-tree etherchannel guard misconfig global config command.
This is the reason it is strongly recommended to use a dynamic negotiation protocol to allow the switches to negotiate the port channel and verify if the links are eligible for bundling.