Reproduction steps:

1. Open "MazeCrusherGame.zip" project
2. Make Scene and Game view visible at the same time
3. Enter "Testlevel" scene
4. Go to Resources>Art>Characters>Char_Knight prefab editor
5. Enter Play Mode.
6. Walk around with WASD keys and notice, that sometimes you push Knight Prefab in the Scene View out of position.

Expected result: Characters, displayed in Scene view do not change position.
Actual result: Knight prefab moves out of position, falls down, rotates.

Fixed in: 2019.1.0a7
Reproduced with: 2018.3.0b1, 2018.3.0b5, 2018.3.0b6
Can not reproduce with: 2018.3.0a9 and lower.

Notes: When entering Play Mode in prefab editor, the game is unplayable, because the main character being constrained like it was in the prefab editor scene.