To reproduce:

1. Download attached project "VideoPlayer5KBug.zip" and open in Unity
2. Open "main" scene
3. Enter Play mode
4. Close the connection between the client and the server while the video is playing

To reproduce from a scratch:

How to reproduce :
1. Create a project with a VideoPlayer
2. Configure the VideoPlayer to play a video from a remote server.
3. Enter Play mode
4. Close the connection between the client and the server while the video is playing.

Expected Result: VideoPlayer.errorReceived event is fired like it is said in the documentation:
"Errors such as HTTP connection problems are reported through this callback."
Actual Result: VideoPlayer.errorReceived event is not fired.

Notes:
- This issue appears on both Windows and OSX
- Steps to reproduce expected result:

1. Close the connection between the client and the server
2. Enter Play mode

Reproduced on Unity 5.6.4p4, 2017.1.2p3, 2017.2.1f1, 2017.3.0f2 and 2018.1.0a7
On Unity Unity 5.6.4p4 and 2017.1.2p3 event is not fired nor when the Internet connection is closed before entering Play mode, nor when you entered Play mode.