How to reproduce:
1. Open the "IN-135782" project
2. Open the "SampleScene" scene
3. In the Hierarchy window, expand the “Terrain” GameObject
4. Select the “Cube” child GameObject
5. In the Inspector window, on the Transform component, increase the Position X value by “0.001“
6. In the Hierarchy window, select the “Terrain” GameObject
7. In the Inspector window, on the NavMesh Surface component, click the "UpdateNavMesh" button
8. Observe the Scene view

Actual result: Off Mesh Links (cyan lines) on GameObject (Terrain -> Cube (10)) are deleted
Expected result: Off Mesh Links (cyan lines) on GameObject (Terrain -> Cube (10)) remain unchanged

Reproducible with: 2023.2.0a16, 6000.0.71f1 (8308b6469260), 6000.3.11f1 (3000ef702840), 6000.4.0f1 (107f2798865e), 6000.5.0a9 (acc4c1f79cd5), 6000.6.0a1 (b0e692525f04)
Could not test with: 2023.1.0a10 (Project gets stuck on "Initial Asset Database Refresh")

Reproducible on: macOS 26.3 (M1 Max)
Not reproducible on: No other environments tested

Workaround: Move the cubes by a small amount before each “UpdateNavMesh“ update