Switched PHP 5.6 to PHP 5.5 and working fine. Except it is showing scanned pages twice as following:
332308 | 6597 | 10,271,133.0 | 30:59:26 | 0:36:54 | 15 | 196,935.8 Kb | 109872 | 14466 | 2
332308 | 6597 | 10,271,133.0 | 30:59:26 | 0:36:54 | 15 | 196,936.1 Kb | 109872 | 14466 | 1
332309 | 6596 | 10,271,168.2 | 30:59:26 | 0:36:54 | 15 | 196,939.0 Kb | 109873 | 14467 | 3
332309 | 6596 | 10,271,168.2 | 30:59:27 | 0:36:54 | 15 | 196,939.2 Kb | 109873 | 14467 | 0
so, it's taking twice the time..