1. Download the attached project
2. Using terminal, navigate to the project root folder
3. Run this command ~20 consecutive times: "{PATH TO UNITY}/Editor/Tools/FSBTool/FSBTool" -c aac -C aac -q 100 -s 44100 -h Temp/fsbankcache -l "{PATH TO UNITY}/Editor/Tools/FSBTool" -i Assets/gameKeyLockDestroyed.mp3 -o Temp/importedAudioTempPrimary

Result: FSBTool freezes

Reproduced on:
* 5.6.3p4, 2017.1.1p3, 2017.2.0b9, 2017.3.0b2 (macOS)
* 5.6.3f1, 2017.1.1f1, 2017.2.0b11, 2017.3.0b1 (Linux)

Note: you can use test.sh file in the root project folder (which loops the FSBTool command) for easier reproduction