Regression from Version 5.4.4p2 (53da848b487a)
Cannot reproduce it without Perforce, but according to stack trace assigned to Scene Management.

Steps:
Prerequisites:
1. Create a scene with prefab (e.g. cube) on it
2. Submit the project to Perforce
3. Get this project on a second machine

Steps:
Computer2:
1. Open scene and change position of the prefab
2. Save scene and submit

Computer1:
1. Open the same scene and change the position (to some different values ) of the same prefab
2. Save scene and submit
==>
Conflict appears

3. Resolve conflict by choosing "merging" -> accept mine
4. Confirmation window appears asking for reloading scene (by the way it shows two scenes with the same name, it is strange)
5. Agree to reload scene
==>
Editor crashes