1. What happened
After exporting unity package, Editor hangs/crashes.

Attaching Editor log and crash call stack from case, when Editor actually crashed for the same case. Otherwise, it hangs for the description below.

2. How we can reproduce it using the example you attached
See attached video or here: https://monosnap.com/file/w07srb2dUv6mwvbghoSwN83gyJrD9r
- Open Scene 1
- Right-click on SpaceStone_Huge_v11.prefab in project explorer
- Export
- Return to Editor
---> It becomes unresponsive.

Sometimes it doesn't happen straight away. Need to make a number of tries. But it happens eventually. 'Might' be related to a number of objects in the scene.

Wasn't able to repro this in 5.5.1f1