Redis's Redisson's API method .unlock() is not releasing the lock, trying from the same instance

I have created singleton redisson instance in my Java application, which I am using to communicate to redis servers.Now using this redisson instance, I am acquiring a lock which after getting some task done, I am releasing. But after calling unlock method, I still see redis have the lock and other threads are unable to acquire the lock.Below is the code snippet, I am using:

class RedisInstance{   static RedisInstance ins;   private RedisInstance()     {       ins = new RedisInstance();     }   public static RedisInstance getInstance()     {       return ins;     }   //Acquire the lock:      public boolean acquireLock(String lockKey)     {         RLock redisLock = getRedisClient().getLock(lockKey);         boolean isLockFree;         try          {            isLockFree = redisLock.tryLock(lockAcquistionTimeLimit, TimeUnit.SECONDS);            if(isLockFree)            {                 redisLock.lock();                 logger.info("lock acquired for: {}", lockKey);                 return true;            }         }          catch (InterruptedException e)          {             logger.error("Got exception {} in acquiring Redis Lock for: {}" , e, lockKey);         }         return false;     }   //Release the lock:   public void unlock(String lockKey)     {         RLock redisLock = getRedisClient().getLock(lockKey);         redisLock.unlock();         logger.debug("IS redis locked "+redisLock.isLocked());         logger.info("lock released for: {}", lockKey);     }}

class A{   RedisIns ins = RedisInstance.getInstance();   public void run()         {        if(ins.acquireLock(lockKey))                {                    try                     {                        //do some processing takes less than a second                           }                    catch(Exception e)                    {                    }                    finally                    {                        ins.unlock(lockKey);                    }                }         }   //In my main method:   public static void main(String args[])   {     A a = new A();     A b = new A();     Thread t1 = new Thread(a);     Thread t2 = new Thread(b);     t1.start();     Thread.sleep(5000); //just to mock, lets say t1 finishes before t2 starts     t2.start();   }}

After t1 calls ins.unlock(lockKey);, the log logger.debug("IS redis locked "+redisLock.isLocked()); says: true and t2 is unable to acquire the lock.

But if I replace redisLock.unlock(); with redisLock.forceUnlock(); everything is working as expected.Dont know why unlock() is unable to release the lock forceUnlock() is able to do it.