Error We were unable to load this page.

I saw "Error We were unable to load this page" error after i clicked the "diff" tab to see if i have a conflict. I don't know how to fix it. Looking in Chrome developer tools on console tab I can see 2 request link and when i check the first it was a 404 page, and another link return a json message {"type": "error", "error": {"message": "[Errno 28] No space left on device",... Is it about my device? I have more space so I think its not..