Finding MAC address of an offending device that triggers BPDU guard

I'm trying to detect an offending MAC address of a device that is connected to a user LAN port, which keeps sending BPDUs every 2 minutes. BPDU guard is enabled on the port and error disables the port every two minutes.

The following commands did not yield the offending MAC address.
debug spanning-tree switch rx decode
debug spanning-tree switch rx process

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The log showed as follows:

Oct 15 16:05:41.971 EDT: %PM-4-ERR_DISABLE: bpduguard error detected on Gi1/0/31, putting Gi1/0/31 in err-disable state

Oct 15 16:07:41.958 EDT: %PM-4-ERR_RECOVER: Attempting to recover from bpduguard err-disable state on Gi1/0/31

Oct 15 16:07:53.403 EDT: %SPANTREE-2-BLOCK_BPDUGUARD: Received BPDU on port GigabitEthernet1/0/31 with BPDU Guard enabled. Disabling port.

The two debug commands yielded the following output:

Oct 15 15:49:46.501 EDT: STP SW: PROC RX: 0100.0ccc.cccd<-1880.900a.9a80 type/len 0032

Oct 15 15:49:46.501 EDT: encap SNAP linktype sstp vlan 200 len 64 on v200 Gi1/1/1

Oct 15 15:49:46.501 EDT: AA AA 03 00000C 010B SSTP

Oct 15 15:49:46.501 EDT: CFG P:0000 V:02 T:02 F:3C R:80C8 1880.900a.9a80 00000000

Oct 15 15:49:46.501 EDT: B:80C8 1880.900a.9a80 80.81 A:0000 M:1400 H:0200 F:0F00

Oct 15 15:49:46.501 EDT: T:0000 L:0002 D:00C8

Oct 15 15:49:47.512 EDT: STP SW: PROC RX: 0100.0ccc.cccd<-1880.900a.9a80 type/len 0032

Oct 15 15:49:47.512 EDT: encap SNAP linktype sstp vlan 10 len 64 on v10 Gi1/1/1

Oct 15 15:49:47.512 EDT: AA AA 03 00000C 010B SSTP

Oct 15 15:49:47.512 EDT: CFG P:0000 V:02 T:02 F:3C R:800A 1880.900a.9a80 00000000

Oct 15 15:49:47.512 EDT: B:800A 1880.900a.9a80 80.81 A:0000 M:1400 H:0200 F:0F00

Oct 15 15:49:47.512 EDT: T:0000 L:0002 D:000A

If the offending devie is an unmanaged layer 2 switch, would there still be a MAC aaddress? Any suggestions on other commands I could to find the offending MAC address?

Thanks,
corehazard

I am not able to use SPAN on the switch.