请问为何重复发送

[ap0405140]

运行环境:
Windows10
MYSQL 8.0.33
canal 1.1.7
canal c#: CanalSharp 1.2.1

问题重现:
在mysql执行以下代码(逐句执行)
create table tab0919
(
x1 binary(10),
x2 datetime,
x3 bool,
y varchar(100),
constraint pk_tab0919 primary key(x1,x2,x3)
);

insert into tab0919 select 0x123F,now(),101,'ddd';

insert into tab0919 select 0x123F,now(),102,'ddd';

update tab0919 set x2=now();

alter table tab0919 modify column x1 varbinary(34) not null comment 'xx not null';

insert into tab0919 select 0x123F,now(),103,'ddd';

alter table tab0919 rename column x1 to x1B,rename column x2 to x2B;

alter table tab0919 rename column x1B to x111B;

==> 以上SQL都能正确解析,都已Ack确认过. 但是当执行以下SQL:

insert into tab0919 select 0x123F,now(),104,'1122';

==> 得到的Header.EventType=EventType.Alter,
包含2个SQL:
alter table tab0919 rename column x1 to x1B,rename column x2 to x2B;
alter table tab0919 rename column x1B to x111B
即是前面执行过的SQL, 重复执行该SQL导致报错了! 请问为何重复发送, 前面已接收过一次了, 且已Ack确认过, 还重复接收一次.