the parent node never delete cause thousands of parent node

[hahahng]

hello
zookeeper version :3.4.13
curator:4.2.0
our project the such similar code

 lock = new InterProcessMutex(client, LOCK_PATH_PREFIX + userid);
                acquire(lock);
try{
}catch(){}finally{
lock.release()
}

but we found the parent node LOCK_PATH_PREFIX + userid never delete

i read the the answer of stackoverflow
but not details ,can u offer detail answer in zookeeper version 3.4.13