Reproduction steps:
1. Open project "MobileBoardCoreGames.zip"
2. Open Scene "Board"
3. Build and run

Expected result: no crash
Actual result: crash when opening the app

Reproducible with: UI Toolkit 1.0.0-preview.13 (2020.2.0f1, 2021.1.0a10)
Not reproducible with: UI Toolkit 1.0.0-preview.13 (2020.1.16f1)
Can't test with: 2018.4, 2019.4 (do not support UI Toolkit)

Stacktrace (Android):
(DynamicHeapAllocator::Allocate(unsigned int, int)+420)
(MemoryManager::Allocate(unsigned int, unsigned int, MemLabelId const&, AllocateOptions, char const*, int)+156)
(MemoryManager::Allocate(unsigned int, unsigned int, MemLabelId const&, AllocateOptions, char const*, int)+448)
(MemoryManager::Allocate(unsigned int, unsigned int, MemLabelId const&, AllocateOptions, char const*, int)+448)
(malloc_internal(unsigned int, unsigned int, MemLabelId const&, AllocateOptions, char const*, int)+40)
(core::StringStorageDefault<char>::reallocate(unsigned int)+80)
(core::StringStorageDefault<char>::resize(unsigned int, bool)+42)
(void StreamedBinaryRead::TransferSTLStyleArray<core::basic_string<char, core::StringStorageDefault<char> > >(core::basic_string<char, core::StringStorageDefault<char> >&, TransferMetaFlags)+42)

Notes:
- Crash does not reproduce when UI Toolkit package is removed and imported again
- Cannot reproduce when rebuilding the Scene in a different project
- Could not produce a useful stacktrace with Player on Windows
- Turning off and on the project solves the issue