I have seen this happening in one of the older cases where following happened: (in a RBR scenario)
M1 <----> M2 in dual replication topology.
However, somehow a change master got executed which pointed M1 to M3 resulting in:
M3 ---> M1 ----> M2 ('--->' is master-of relation).
After sometime this was rectified, however, the binlog on M1 recorded events with server_id of M3 -- lets call it 3
after rectification, it again became M1 <------> M2
So, binlog events with server_id 3 ping-ponged between M1 and M2.
I have seen this happening in one of the older cases where following happened: (in a RBR scenario)
M1 <----> M2 in dual replication topology.
However, somehow a change master got executed which pointed M1 to M3 resulting in:
M3 ---> M1 ----> M2 ('--->' is master-of relation).
After sometime this was rectified, however, the binlog on M1 recorded events with server_id of M3 -- lets call it 3
after rectification, it again became M1 <------> M2
So, binlog events with server_id 3 ping-ponged between M1 and M2.