Reproduction steps:
1. Open the attached “repro_IN-102999“ project
2. Open the “Assets/Scenes/Game.unity“ Scene
3. Ensure that Domain Reload is enabled when entering play in the Unity settings.
4. In the Editor, enter the Play Mode
5. Main Editor window crashes

Reproducible with: 1.4.3 (6000.0.50f1, 6000.1.5f1, 6000.2.0a3)
Couldn’t test with: 2021.3.52f1, 2022.3.62f1 - “Multiplayer Play Mode“ package doesn’t exist in these Editor versions

Reproducible on: macOS Sequoia 15.5 (M3 Pro), Windows 11 (23H2) (reporter’s environment)
Not reproducible on: No other environments tested

First few lines of the stack trace on macOS:
#0 0x00000105af3ebc in TypeTreeQueries::IsStreamedBinaryCompatible(TypeTreeIterator const&, TypeTreeIterator const&)
#1 0x00000106ded564 in GenerateUndoAndRedoDiffs(RecordedObjectList&, core::vector<UndoPropertyModification, core::allocator<UndoPropertyModification, 0ul>>&, core::vector<UndoPropertyModification, core::allocator<UndoPropertyModification, 0ul>>&)
#2 0x00000106e0a20c in PropertyUndoManager::Flush()
#3 0x0000010682c000 in Application::TickTimer()
#4 0x00000107bedcb8 in -[EditorApplication onEditorUpdatesTickTimer]

First few lines of stack trace on Windows:
0x00007FFE82A59B8A (Unity) TypeTreeIterator::GetNode
0x00007FFE82A88508 (Unity) TypeTreeQueries::IsStreamedBinaryCompatible
0x00007FFE83BE5DC2 (Unity) GenerateUndoAndRedoDiffs
0x00007FFE83BF1B1C (Unity) PropertyUndoManager::Flush
0x00007FFE83723FBD (Unity) Application::TickTimer