Steps to reproduce:

1. Open the attached project
2. Open 'scene'
3. Press play
4. Ensure that drawing gizmos is enabled, so that debug lines can be seen
5. Watch as the cube slides along the rail, the cube will either slide off the end of the rail, or hit the rail, bouncing the cube in the air
6.1. If the cube collides with the rail, there will be debug lines draw at the point of the collision
6.2. If it doesn't collide, the cube will reset, giving it another chance to collide
7. When it collides there is a chance that the Collision.impulse direction (green lines) doesn't match the direction of change in velocity caused by the collision (blue lines). If this happens, a message is displayed to alert you (in magenta), and the cube won't be reset, so that the bug can be better seen

Note: This will usually take 3 to 4 times of the cube resetting to produce this bug. If you wish to reset after the bug occurs, press 'Space'.

Reproduced with: 5.2.0f3, 5.2.3f1, 5.3.0f1, 5.4.0a2