Generally, this error message is seen when a STP BPDU is received on a local port that has STP disabled. By inference, this means that the connected remote port is sending STP BPDUs to the "STP Disabled" port.
However, this error message persists even when STP is disabled on the remote port as well, if the following conditions are met -
- MSTP is used.
- MSTI and CIST are currently disabled on both the remote port and local port
- If MSTI was enabled at some point in time on the remote port and then disabled (This could even mean that the port was added to MSTI with auto-bind enabled)
Port timer doesn't seem to stop after disabling the MSTI on the STP port causing the remote port to continue sending the STP BPDUs.