Deadlocks(ERROR 1213 (40001)) when running an alter table command

MySQL & MariaDB Other MySQL® Questions
1

When I’m running following SQL, the application which is still live is hitting a deadlock: ERROR 1213 (40001) at line 2: Deadlock found when trying to get lock; try restarting transaction
Query:

ALTER TABLE comm
ADD COLUMN thumb_url varchar(256) NULL DEFAULT NULL COMMENT ‘’ AFTER search_index_version,
ADD COLUMN thumb_src_url varchar(256) NULL DEFAULT NULL COMMENT ‘’,
LOCK = NONE;

When I read the mysql 5.6 documentation it shouldn’t lock, or am I wrong?

Version:Server version: 5.6.27-76.0-56-log Percona XtraDB Cluster (GPL), Release rel76.0, Revision 2a6d4e5, WSREP version 25.13, wsrep_25.13

Any pointers here?

Thanks in advance for your assistance!