Investigators knew underwater signals invalid, yet they chose to waste 8 weeks investigating them

The MH370 Search Areas Report dated June 26, 2014 proves the fact that the Investigators knew the underwater signals detected by Ocean Shield were invalid, yet they chose to waste 8 weeks investigating them.

It is also a fact that prior to the detection of those underwater signals, the Investigators leading the search for MH370 already knew Inmarsat's "hotspot" location for MH370. 

From the June 26 report:

The flight recorders fitted to 9M-MRO were equipped with Dukane DK100 underwater acoustic beacons that activate on immersion in salt or fresh water. The beacons had the following characteristics:
- Operating frequency: 37.5 ± 1 kHz
- Pulse Length: 10 ms
- Repetition rate: 1 pulse per second
- Operating life following immersion: minimum 30 days

The ADV-OS deployed the first towfish on 4 April 2014. The first towfish exhibited acoustic noise and was required to be changed out with the second towfish. The second towfish was deployed on 5 April 2014 and shortly after, whilst descending, detected an acoustic signal at a frequency of approximately 33 kHz. Further detections were made on 5 April 2014 and on 8 April; however, none were able to be repeated when following an opposing track. The first towfish was redeployed with no detections.

A review of the Ocean Shield acoustic signals was undertaken independently by various specialists. The analyses determined that the signals recorded were not consistent with the nominal performance standards of the Dukane DK100 underwater acoustic beacon. The analyses also noted that whilst unlikely, the acoustic signals could be consistent with a damaged ULB. However, it was decided that that an ocean floor sonar search should be performed to fully investigate the detections.