If the loading bar turns red, an error occurred loading one of the images and the browser error console (ctrl+shift+j) will have more information. Commonly this is just because you forgot to upload one of the images and does not mean it's a C2 bug. What does the browser console say and can you link us to the uploaded demo that is not working?
You are right. Pictures not load correctly because of "not allowed" characters in name. Maybe not supported characters should be restricted in C2 because of this.
BTW. Why sometimes is fast movement not smooth even with 60fps? If you create "hockey" arena and small ball inside (walls have Solid behaviour) with Bullet behaviour - for example speed to 1000. Smooth of movement change (not speed) and it looks bad. Debug and FPS not show anything wrong. Is it normal? Tested in Chrome, Opera, Firefox.
AND WHY you remove some sections from manual? I have older one with Multiplayer etc. New one have missing them - only Websocket is there. Why?
And Send to Peer work only as Host. If you are Peer and want send message directly to another Peer, message not arrive. Only from Host.