Reproduction steps:
1. Open the attached project "ReproProj"
2. Open the “/Assets/Content/Cluster/Cluster.unity” Scene
3. In Hierarchy, expand the “ClusterCanvas”
4. Expand the “TabBar“
5. Select “HighlightLine“
6. In Inspector, drag the “Pos X” to the right to increase its value to something like 200
7. In Hierarchy, Drag the “HighlightLine“ on “TabContainer“ to parent it
8. Press “CTRL + Z“ to Undo
9. Select “HighlightLine“
10. Observe “Pos X“ in Inspector

Expected result: “Pos X“ is not grayed-out and can be edited
Actual result: “Pos X“ is grayed out

Reproducible with: 6000.0.64f1, 6000.3.2f1, 6000.4.0a5, 6000.5.0a3

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested