Fuel trucks not completing fuel round

A feul truck full of fuel, refulled and plane and then with low fuel returned back to the deopt. The next plane it refules as it does not have enough fuel on board, the fuel service round does not get to 100%.

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COLLECTED HARDWARE DATA
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Device
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Model: iMac17,1

Operating system: Mac OS X 10.13.0

RAM size: 24 GB

Battery status: Unknown
Battery level: -1

Processor Device
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Type: Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
Core count: 8
Frequency: 4 GHz

Grahpics Device
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Vendor: Apple
Type: AMD Radeon R9 M395X
Memory Size: 4 GB

Screen Summary
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Full Screen: True
Resolution: 5120 x 2880 @ 60Hz