How to reproduce:
1. Download the attached project
2. Download the "UBM.zip" and put the extracted folder to the Assets folder
3. Download the "Build.sh" script and change it's content with pathes relevant to your machine
4. Make sure Unity have Android and iOS setup
5. Run the Build.sh script
6. Wait

Actual result: Unity crashes.

Reproduced on: 2019.2.3f1.

Notes:
- The crash is very rare to reproduce. (Reproduced only once by Unity team)
- The script is building the project for iOS and Android on a permanent loop while also switching between versions.

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Fixed in 2020.1.0a10.