Error Generating Graphs in Unity 6000.1.0b1 (A* Pathfinding Project Pro 5.3.1)

I created a grid graph and received this message when scanning:

There was an error generating the graphs:
UnityEngine.Assertions.AssertionException: Assertion failure. Value was False
Expected: True
at UnityEngine.Assertions.Assert.Fail (System.String message, System.String userMessage) [0x00043] in :0
at UnityEngine.Assertions.Assert.IsTrue (System.Boolean condition, System.String message) [0x0000f] in :0
at UnityEngine.Assertions.Assert.IsTrue (System.Boolean condition) [0x00009] in :0
at Pathfinding.Jobs.JobDependencyTracker.Dispose () [0x00000] in .\Packages\com.arongranberg.astar\Utilities\JobDependencyTracker.cs:448
at Pathfinding.Jobs.JobDependencyTracker.ClearMemory () [0x0000e] in .\Packages\com.arongranberg.astar\Utilities\JobDependencyTracker.cs:460
at Pathfinding.GridGraph+GridGraphUpdatePromise+d__22.MoveNext () [0x00eca] in .\Packages\com.arongranberg.astar\Graphs\GridGraph.cs:2031
at Pathfinding.GraphUpdateProcessor.PrepareGraphUpdatePromises (System.Collections.Generic.List`1[T] promises, Pathfinding.Jobs.TimeSlice timeSlice) [0x000cf] in .\Packages\com.arongranberg.astar\Core\Pathfinding\GraphUpdateProcessor.cs:244
at AstarPath+d__128.MoveNext () [0x002e2] in .\Packages\com.arongranberg.astar\Core\AstarPath.cs:1782
at AstarPath+d__126.MoveNext () [0x00046] in .\Packages\com.arongranberg.astar\Core\AstarPath.cs:1656
at Pathfinding.AstarPathEditor.MenuScan () [0x00072] in .\Packages\com.arongranberg.astar\Editor\AstarPathEditor.cs:1291

If you think this is a bug, please contact me on forum.arongranberg.com (post a new thread)

UnityEngine.Debug:LogError (object)
Pathfinding.AstarPathEditor:MenuScan () (at ./Packages/com.arongranberg.astar/Editor/AstarPathEditor.cs:1304)
Pathfinding.AstarPathEditor/<>c__DisplayClass74_0:b__0 () (at ./Packages/com.arongranberg.astar/Editor/AstarPathEditor.cs:789)
UnityEditor.EditorApplication:Internal_CallUpdateFunctions ()

That’s strange. Did this only start to happen after upgrading to a newer version of Unity?

Yes, when I upgraded from 6000.1.0a9 to 6000.1.0b1.