Debezium mySQL connector not able to acquire global read lock

I'm using Debezium mySQL connector to get CDC data from a 3-node xtraDB database. Its worked for other databases in the past, but for some reason, the connector to the current database is unable to acquire global read locks. The fall back option of using TABLE LOCKS if acquiring GLOBAL READ LOCK fails does not work given the way xtraDB is set up, so if the connector fails to acquire GLOBAL READ LOCK, it fails entirely. I want to re-produce this error in a dev environment but I can't figure out how to force a FLUSH TABLES WITH READ LOCK to fail. Anybody got any ideas on what cause FLUSH TABLES WITH READ LOCK to fail (locks not getting acquired) in a mySQL database and how I may reproduce it? I tried starting a transaction on one node to UPDATE a particular column value of a row in a table but not committing the transaction so it remains open with a row lock. I then started another session using the same DB user connecting to the same DB node and tried FLUSH TABLES WITH READ LOCK. I was hoping that would not succeed as I thought the UPDATE would still be having a lock which would block the FLUSH TABLES WITH READ LOCK statement, but it did not.