Steps to reproduce:
1. Download and open the attached project
2. Open Scene "Main"
3. Try to move Canvas in scene view with Z axis arrow - Notice it moves, see the attached gif "ClipingUI.gif".

Notes:
Notice Screen Space - Overlay coordinates are locked in inspector, but changes when moving Canvas on Z axis in scene view.

Other notes:
Moving X or Y axis in scene view is locked as it should be.
Moving Screen Space - Camera Canvas in scene view coordinates are changing in inspector.

Reproduced with: 5.2.4f1, 5.3.4p2, 5.4.0b14.