How to reproduce:
1. Open the attached project "PerfBug.zip"
2. Open the "SampleScene" scene
3. Select navmesh prefab object
4. Use the ProBuilder edge tool to move an edge
Expected result: The editor does not lock up
Actual result: The editor locks up for 20-30 seconds
Reproducible with - 5.0.1(2020.3.3f1), 5.0.1(2021.1.2f1), 5.0.1(2021.2.0a12), 5.0.4(2022.2.0a1)
Could not test (project did not load) - 2018.4, 2019.4
Notes:
1. Entering Play Mode also produces ~20s wait time to load and exit
2. Removing the prefab version from the scene makes the delay disappear