Aircraft can sometimes get stuck waiting for runway to clear when there are no planes using the runway

Airplanes started to suddenly queue up without any sane reason. The same config worked well for days, and then, suddeny, everything stuck.

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COLLECTED HARDWARE DATA
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Device
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Model: To Be Filled By O.E.M. (To Be Filled By O.E.M.)

Operating system: Windows 10 (10.0.0) 64bit

RAM size: 8 GB

Battery status: Charging
Battery level: -1

Processor Device
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Type: Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz
Core count: 4
Frequency: 3 GHz

Grahpics Device
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Vendor: ATI
Type: AMD Radeon HD 6900 Series
Memory Size: 2 GB

Screen Summary
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Full Screen: True
Resolution: 1920 x 1200 @ 60Hz